Billy's pet hamster, Mr. Snuggles, celebrates his 10th birthday, so the Grim Reaper comes for him. However, Mandy, Billy's friend, is reluctant in allowing it, so she proposes a deal to the Grim Reaper: if he beats the kids in a game, he can take the hamster, but if he loses, he will spare the hamster's life and become their "best friend forever". The Grim Reaper transports the kids to limbo, where he challenges them to a game of limbo. Despite his best effort, Grim ends up losing because he is attacked by Mr. Snuggles at Mandy's command.
Billy and Mandy tell Grim it is "Opposite Day" and that, when they say something, they really mean the opposite. Due to his difficulty understanding the concept of Opposite Day, Grim has to do Mandy's chores. Finally, Grim thinks he understands when Billy and Mandy say they "want" pie, meaning they "do not want" pie. However, Mandy then says that when she said it was Opposite Day, it really was not.
Billy's mother, Gladys, first notices Grim in Billy's bed, then in the shower and subsequently starts to get panic surges thinking that Billy is in danger. Meanwhile, Harold, Billy's dad, just thinks that Gladys is imagining things. In the end, Gladys ends up going living with Billy's aunt, Sis to try and calm herself down.
After watching a movie, Grim teaches Billy to possess people by jumping into their heads. Billy possesses Mandy and makes her do assorted things like flirting with Irwin, kissing Mandy's mother, going into both men's and women's restrooms and eating earthworms. In the end, Billy leaves Mandy's head, but later that night, Mandy possesses Billy's cat, Milkshakes, to maul him as a form of revenge.
Grim misses his life as the reaper of souls and, due to his bet, he cannot return to the Underworld, much to the hilarity of his Underworld co-workers. Having a sudden epiphany, Grim decides to be good and help people rather than try to take their souls. However, Grim's attempts at being good are faced with resistance from people, who are scared off by his appearance.
Grim is bored of being left alone while Billy and Mandy are not with him. Grim decides to fulfill his dream by working as a swimsuit model, but, as he is a corpse, he isn't hired. Subsequently, Billy and Mandy give him a makeover to look more human. In the end, Grim gets the job in a TV ad, but he is only in the commercial for a few seconds and is portrayed as an ugly person.
Billy wanders into a junkyard, where a massive hole in the earth opens up and pulls him down in. Later, Mandy and Grim get pulled in as well. They land at the center of the Earth, which is home of Nergal, a devilish creature. The lonely Nergal, who has been watching Billy and Mandy for some time, wants Grim to hand over the kids to him so they can be his friends forever. Grim happily leaves the kids behind as he returns to the surface; however, he later goes back for them because he can't handle the guilt of abandoning his friends. In the end, Grim is defeated by Nergal's electrified tentacles, but Mandy defeats Nergal merely by kicking him in the shin.
Billy, Mandy, Grim and Pud'n are part of the "Person Scouts" (a Boy Scouts-esque organization) and need to sell cookies in order to win a badge. However, as Billy eats all of the cookies, Grim proposes to bake their own cookies using his aunt Kali's secret recipe. The cookies are a success and the troupe wins the contest. In the end, at the Person Scouts awards' ceremony, aunt Kali reveals that the secret recipe contains insects, but everyone continues eating the cookies anyway.
While Spring cleaning in the middle of November, Billy takes an old, cursed lamp from Grim's trunk. When he gives it a rub, he releases the curse Grim had warned them about: his own mother. Having three wishes to make, Billy wastes his wish by wishing to know what to wish for. Mandy wishes Billy and Grim would "shut up", so Grim never gets to make his wish. Then, Mandy decides to make the last wish to whoever makes her the happiest. In the end, Mandy wishes everyone in the world would go away, which she is glad about.
After having a nervous breakdown and leaving the house in the first episode, Billy's mother, Gladys, returns. She meets Grim again and, this time, she plans to destroy him once and for all. When Grim goes to the kitchen for a glass of water, Gladys attacks him and shatters his skeleton. In the end, Grim assures the kids that Gladys has won the battle but not the war.
It's Halloween, Billy, Mandy and Grim go trick-or-treating. Grim mistakes a woman for Atrocia, the host of the all-night Halloween marathon on TV and goes to talk to her. Upon looking at her face, Grim realizes his mistake; however, the woman mistakes Grim for her son, Gregory, and takes him home. At the same time, Billy mistakes Gregory for Grim and he and Mandy take him with them. In the end, Billy and Mandy take Gregory back to his mother and Grim goes back with them.
With Irwin not answering the phone, Billy's parents missing and Mandy saying she wants "Billy for dinner", Billy and Grim assume Mandy is a cannibal who ate Billy's parents and friends. Looking for proof, Billy and Grim find tiki figures and arrangements for a celebration in Mandy's backyard. Ultimately, it is revealed that they are just celebrating Billy's birthday. Still, Mandy burps out Irwin's glasses.
Billy and Irwin have been playing their favorite video game, Beasts and Barbarians, for three days non-stop. In an attempt to stop their video game addiction, Grim transports them all to a real-life version of the game. Seeing as Billy and Irwin are still doing good in their quest, Grim increases the difficulty by manipulating the traps himself. In the end, Billy, Mandy, and Grim return home escaping from a giant cyclops, while Irwin remains trapped.
Billy tells Grim to help him throw a surprise birthday party for Mandy. Then, a reluctant Grim helps Billy prepare a cake while keeping it a secret from Mandy. In the end, a somewhat surprised Mandy reveals that her birthday isn't for the next five months, something that Billy already knew about.
Nergal, the fiend from the center of the Earth, returns to the surface, emerging a carnival with him, trying once more to make friends. In the following, Billy tries to help Nergal make friends by being considerate, but Nergal fails to apply correctly his advice. When Nergal is told that Grim was forced to be Billy and Mandy's friend-slave, Nergal then decides to force the world to be his friends by turning them into dark beings similar to him. In the end, Nergal turns Billy, Mandy, Grim and even the viewer (thus breaking the fourth wall) into one before the episode ends.
Billy, Mandy, and Grim go to the museum on a school trip. There, they meet Hoss Delgado, self-appointed hunter of the paranormal, who upon spotting Grim, tries to eliminate him. Subsequently, Grim and Delgado engage in a fight. Finally, Delgado quits hunting Grim when he realizes Billy and Mandy control him. In the end, Delgado continues his adventures and is seen fighting a werewolf.
Mandy and her parents leave the city for a day, which makes Billy feel lonely. Then, Grim uses his supernatural powers to create a fake Mandy with pieces of dolls and toys for Billy to play with. However, the "new" Mandy is too aggressive with Billy, and he starts fearing her. The next day, the real Mandy returns home, and promptly destroys the new Mandy while in the see-saw.
Billy eats too much junk food that makes him feel sick. Grim prepares him a remedy using his granny's recipe, but this medicine makes a parasite to start growing in Billy's back, which Billy names Yap-yap. In the following, Billy and Yap-yap continue eating junk food, so Mandy suggest to use the antidote to the original remedy. Eventually, Yap-yap, now looking like a smaller version of Billy, detaches himself from Billy (which would have technically cured Billy without the need of him drinking the anitdote), and tries to escape from the antidote. In the end, Yap-yap drinks the antidote and is destroyed.
While going to the shopping mall with Billy and Mandy, Grim spots the beautiful Eris, the goddess of discord and chaos, and tries to ask her out. However, Eris is not interested in the skinless Grim, but in the muscular Adonis. Then, Eris invites Mandy to join her in creating chaos using the Apple of Discord. Although initially they get along, Eris pulls a prank on Mandy, who subsequently tries to get revenge. In the end, Mandy fools Eris into thinking that Adonis is in the movie theater, and Eris accidentally kisses Grim.
Billy is constantly provoked by a bully named Sperg and runs over to Grim for help.
After taking the Underworld's "Bad Book" from Grim, Billy becomes possessed by an evil entity. Then, Billy steals Grim's scythe, and uses it to open a portal to summon Yog-Sothoth. In consequence, Mandy calls for Hoss Delgado to battle Billy. It is revealed that the portal can only be sealed by throwing the book into it. As Billy eats the book, Mandy throws Billy himself into the portal, restoring everything to normal. Instants later, a portal opens up and Billy comes out saying that they didn't want him there.
Billy wants to join Sperg's garage band, "Purple Filth", and take part in the upcoming battle of the bands. However, after witnessing Grim's prowess with the electric guitar, Sperg invites Grim instead. Then, Billy's dad, adopting the rock and roll persona of "Mogar", decides he and Billy should go to the contest to make a surprise appearance. In the end, Billy impresses the audience with his armpit sounds.
Billy, Mandy, and Grim eat moldy pizza leftovers, and after falling asleep, they have nightmares. Billy dreams of cute bunnies which turn into monsters; Grim dreams of an endless number of bossy Mandys; Mandy dreams of being pulled into a volcano and then commanding demons at the rhythm of music, in a scene that reminisces the Night on Bald Mountain segment of Fantasia. In the end, Mandy reveals that her dream was actually very pleasant, and she eats the last slice of the rotten pizza.
In this musical episode, which pays homage to Little Shop of Horrors, Billy befriends a brain-eating meteor that falls from the sky. With Billy's help, the creature grows bigger and eventually eats the brains of all people in Endsville (turning them into zombies with glowing green eyes). The last brain he eats is Mandy's, which results in the creature transforming into a brain-eating Mandy. The song featured is BRAINS!, composed by goth artist Voltaire specifically for this episode.
Billy and Mandy take a reluctant Grim to school with them. There, Mandy's nemesis, Mindy, befriends Grim to annoy Mandy. In consequence, Billy calls for their other friend, who is Abraham Lincoln. In the end, Mandy devises a plan in which Mindy ditches Grim, and keeps Abraham as her friend instead.
In a parody of the Harry Potter series, Grim sends Billy and Mandy to a sorcery school so the latter duo could avoid boring summer camps they were supposed to go to. The sorcery school is owned by Dean Toadblatt, an anthropomorphic frog. Billy and Mandy are sent to the most hated house on the school, Weaselthorpe, while Grim becomes a prefect for a more loved house, Gunderstank. Billy and Mandy then team up with boy wizard Nigel Planter to sabotage Gunderstank. During the episode, Planter takes all the credit for the sabotage (which was Mandy's idea in the first place), but in the end, he is punished for it once he is "accidentally" found out by Toadblatt.
After watching Billy and Irwin play with their "Hokey Monsters" cards (parodying Pokemon), Grim makes the monsters come to life. Soon, all the other kids want their own cards to be real too. Subsequently, the city is under attack by a multitude of Hokey Monsters. To put an end to the mayhem, Mandy draws her own card, Mandy's Monster, which defeats all the other monsters by turning them into toast.
Grim is lying sick in bed with "Encroaching Doom Syndrome". The Underworld doctors are not able to help Grim, and he becomes a human being. Back in Endsville, Grim is apparently attractive to women, but he ends up being punched by jealous boyfriends, especially Billy's dad Harold. In the end, Grim covers himself in the mucus that he produced when he was sick, and becomes a skeleton again. Billy tries it too.
Billy and Hoss Delgado, spectral exterminator, team up to destroy all the zombies that congregate outside the house, but the zombies reassemble into a bigger zombie. Delgado realizes that the zombie is after the brownies that Grim has in his skull, so Delgado and Grim battle furiously for them. In the end, the zombie eats the remaining brownies and then falls apart.
Taking inspiration from his Pat the Baker video game, Billy decides to bake some brownies. However, Billy uses "Evil Powder" from Grim's old trunk instead of salt, and the resultant brownies stink. Mandy tells Grim to get rid of the brownies, and he reluctantly does, but he also stores some of them in his skull. Soon, the stench of the brownies spreads through the world and starts resurrecting dead people, animals, and even food, as zombies.
Billy accidentally sets off a powerful stink bomb in Mandy's house and, while the house is being disinfected, Mandy's family goes to live with Billy's. Then, Billy and Mandy have a dispute over how to split Billy's room, prompting Grim to intervene. In the end, Mandy takes over the entire room, and traps Billy behind a brick wall.
On a hot day when Billy, Mandy, and Irwin are bored, Grim uses a crystal ball to show them the future. In the distant future, Mandy has turned herself into a giant worm-like creature to be immortal, and now rules the whole world. Mandy gives false information to a clone of Billy, in order to capture the members of a resistance that try to defeat her. The episode parodies the science fiction novel God Emperor of Dune by Frank Herbert.
When Billy, Mandy, and Grim go fishing, Eris, the goddess of chaos, gets Billy to help her use the Apple of Discord to create chaos (after her father grounded her). Instead of using the apple, Billy becomes distracted with his own idiotic errands, leading Eris to go insane. In the end, Billy finally decides to start creating chaos, but Eris is already too altered that she runs away.
After Grim fails to pull a werewolf out of his hat, Irwin is bitten by said werewolf. Then, Billy takes Irwin as his new pet dog, naming him Sprinkles, and enters him in the Endsville Dog Show to compete against Mandy's dog, Saliva. At the contest, Sprinkles is about to win, so Grim releases a "were-flea" whose bite causes the werewolf to revert to a naked Irwin. In the end, it appears that Irwin won the contest anyway.
After excluding Mandy from their board game Who Killed Who? for being a girl, Billy and Irwin mistakenly throw their dice into the backyard of a haunted house. Grim warns them about the ghost of Mrs. Doolin, a lady that lived there. Mandy dares to go inside to retrieve the dice, and she befriends Mrs. Doolin, who is alive and well, and who says that all the stories told about her (that anything that went beyond her fence into her garden never came back) are inventions from Grim, whom she beat long time ago at a staring contest. Fearing for Mandy's life, Billy also ventures into the house, but Mrs. Doolin and Mandy scare him away by posing as ghosts. However, it appears that Mrs. Doolin is in fact a ghost, and when she meant "beating Grim", it meant that she "beaten death".
When Billy, Mandy and Grim go to the beach, Grim falls in love with a goth woman named Malaria. Grim is having a good time with his girlfriend, but Mandy assures him that will change when he tells her that he is not human. In the following date, Grim demonstrates his supernatural powers while dancing and, as predicted, Miranda leaves in panic.
It's Valentine's Day and Nergal, the fiend living in Earth's core, appears in Billy's house to court Billy's spinster aunt, Sis. Then, Billy tries ruining Nergal's date, to avoid becoming his nephew. Although initially Sis doesn't show interest in Nergal, she changes her mind when Nergal is stung by bees and she sees his "dance moves". Then, aunt Sis accepts Nergal's marriage proposal, and accompanies him back to the center of the Earth.
At school, Mandy rejects Irwin's invitation to go to the school dance with him. Then, Billy introduces his foreign and mysterious, new friend, "Piff", and Mandy becomes desperate when she realizes she has fallen in love with him. Subsequently, Mandy asks Grim to cut her heart out to stop being in love; however, Grim has a better idea and gives Mandy a makeover. In the end, Piff falls in love with Mandy, and Mandy takes the chance to brutally turn him down.
Grim is upset after his favorite show, Atrocia's Late Night Atrocities, is cancelled. Then, he goes to the TV station and using his powers, turns the studio into a creepier place and becomes the host of the Grim Show. Grim's success on TV is interrupted when Mandy tells him he has neglected to do her chores. Then, Billy and Mandy go to the TV station and show embarrassing footage of Grim at home.
Billy is worried about failing an upcoming Math test, so Grim gives him a "bookworm", which will make him much smarter. However, Milkshakes, Billy's cat, eats the worm instead, and is forced to tutor Billy. In the end, Billy is still an idiot.
Billy takes a big egg found in Grim's trunk and hatches it expecting a duck. Instead, Jeff the Spider is born, who considers Billy his father. Despite Jeff trying to please Billy in any possible way, Billy is terrified of Jeff and wants him squished. In the end, we see that the exterminator didn't squish Jeff because he is a nice bug.
When Billy and Irwin exclude Mandy and Grim from helping them build a go-kart to enter the Annual Endsville Go-Kart Competition, the latter two decide to build their own. At the race, Billy-Irwin, and Mandy-Grim compete against Mindy, Sperg, and a mystery racer (Pud'n). In the end, Mindy gets stuck in highway traffic, Billy-Irwin's car is destroyed, Sperg and Grim mutually prevent each other from winning, and Pud'n wins in his litte red wagon.
After being accidentally hit by Billy, Grim lands in a can of white paint in a remote convent. Due to his appearance, still with the can in his head, Grim is mistaken for "Sister Big Mamma" by little nuns. Then, Grim has a great time with the friendly nuns, until Billy and Mandy come looking for him. When the nuns realize the truth about Grim they get angry at him, but also help him go back home by sending him flying away with another punch.
Billy and Mandy are sent to "Winter Camp", where they meet Nergal's son (and Billy's cousin), Nergal Junior. Just like his father, Junior tries making friends, although not in the best way possible. Junior attacks the campers, freezes them and, using his shape-shifting abilities, takes over their appearances. In the end, Billy decides to be Junior's friend, but he is scared away at the moment Junior shows him his true form.
After missing on a school trip, Grim takes Billy, Mandy and Irwin to the "Halls of Time" for a tour. There, Billy and Irwin mess the hourglasses that symbolize each person's lifespan. When they leave, they accidentally leave their own hourglasses, including Grim's, upside down, resulting in the group getting younger as time passes. In the end, Grim allows the kids to disappear by going before birth, but he can't restore his own hourglass to its correct position and he disappears too.
Grim's refusal to help Mandy win a karate tournament, and the $50 000 dollar prize it promises to the winner, leads her to a curio shop, where the shopkeeper, Kuan Ti, gives her an ancient "Chicken Ball" which, when eaten, allows her to become a great fighter. Subsequently, Mandy easily wins the tournament and doesn't care about the money anymore, only about fighting. It turns out Kuan Ti is actually Eris in disguise, and this was just another of her schemes to create chaos. To stop Mandy, Grim makes Billy a superb fighter too, and he and Mandy fight ferociously until the entire arena is destroyed, (note: this episode is an obvious parody of Dragon Ball Z). In the end, Mandy still demands the prize money, which she uses to buy Hector Con Carne's (from Evil Con Carne) Bunny Island.
After a lousy night for Grim, Billy and Grim argue about who has the hardest time, the kid or the Reaper of Souls. Mandy proposes they switch places for the day to find out. Then, Grim seems to be having a good time, acting like a silly kid, while Billy is bored waiting for his old victim, Mr. Voorhees, to open the door. In the end, Billy transforms into a short skeleton, while Grim transforms into a taller version of Billy.
It's Halloween, and Billy, Mandy and Grim go trick-or-treating, while Irwin is left behind because he needs a scarier costume. After pulling a trick on an old lady, and getting some candies, Grim tells the story of why people pull pranks, which he was partially responsible for. He tells about Jack, a prankster of the old Endsville who just didn't know when to stop. One day, the citizens decided to punish him for his constant pranks, and they pulled a prank on the queen, but signed it "From: Jack"; in consequence, the angry queen sent a knight to kill Jack. However, when Grim went for Jack's soul, Jack stole his scythe. In return for his scythe, Grim promised Jack eternal life, but after closing the deal, Grim cuts Jack's head off. Thus, Jack decided to use a pumpkin for head, becoming Jack O'Lantern, and every Halloween he goes out to pull pranks on the citizens of Endsville. After hearing the story, Billy splits from the group and finds Jack's house downtown. Then, Jack realizes Billy is carrying the actual Reaper's scythe, so he takes it from him and uses it to open the gates of the Underworld and bring forth ghosts, which cause havoc in the city. Jack then plans to get revenge on Grim by cutting his head off which, being cut with the Reaper's scythe, will be cut permanently. To stop Jack from carrying on with his vengeance, Mandy sets up a series of pranks for him. However, the pranks affect Irwin instead, causing major laughter from Jack and his ghouls, which explode and return to the Underworld. In the end, Grim recovers his scythe and sends Jack to the Underworld too.
At a father-and-son picnic, Billy re-encounters with his spider "son", Jeff, in a dirty bathroom. Once again, Jeff tries to make Billy love him, but Billy remains terrified of bugs. Then, Mandy tells Jeff he is being too nice, and in order to get Billy's attention he needs to be meaner. After being coached by Mandy, Jeff finally snaps and ensnares Billy in his spider web, forcing Billy to say he loves him.
When Billy crashes his bicycle, he obtains a free tricycle from a mysterious boy in a supernatural porta-potty. While Billy loves his tricycle, which he calls Trykie, he is also mocked because of it by Irwin, Pud'n and Sperg. Following this, Trykie moves on his own, and attacks the three of them. Later, Mandy realizes the problem with Trykie, and Grim confirms that he is cursed. Finally, Billy realizes that Trykie is evil, and he lets Mandy destroy him once and for all.
Billy, Mandy and Grim go to the beach where Grim falls asleep and Billy buries him in sand. When they leave, Billy only takes Grim's skull, leaving Grim's body to be found by a rich family that take it with them. With his adoptive family, Grim's body becomes a celebrity and refuses to go back with Billy and Mandy. Eventually, Grim's skeleton is reunited with his skull, but instants later it is shattered by dogs.
After spilling salt in a restaurant, and not throwing salt over his left shoulder, Billy starts having an unusual amount of bad luck. The next day, Grim analyzes Billy and finds out he has a "Catastrophe Snail" attached to his brain, which is causing him the bad luck.
General Skarr (originally appearing in Evil Con Carne) buys a home in Endsville and becomes Billy's neighbour. Then, after Skarr invites Billy to his new house, Billy mentions Grim's scythe as the most powerful weapon in the universe, and Skarr tries to battle his desire to be evil again. Eventually, Skarr steals the scythe, but Mandy proves to be scarier than he is and takes it back.
After he turns down his dad's invitation to go fishing, Billy gets a tiny, weakling, pet fish(Arnold Schwarzenegger), which he names Little Porkchop. Then, to make Billy happier, Grim makes the fish grow overnight to become a giant. However, Billy takes Porkchop to play under the Sun, and never gives him water again, so he burns to ashes and is flushed down the toilet. In the end, Billy's dad returns form his fishing trip having caught Porkchop, which returned to his normal size, but plans to cook him.
When Mindy mocks Mandy's dumb and coward dog, Saliva, Mandy decides to train her dog to be meaner. However, after Grim keeps mentioning his own dog, Cerberus, Mandy decides to use Grim's special whistle to call the gigantic, three-headed, fire-breathing hound. In the end, Cerberus marries Mindy's chihuahua, Little Delicious, and Saliva snaps against Mindy for a brief moment.
In this short, set in the Stone Age, a child version of Grim undertakes his first assignments as the Grim Reaper. When he goes to visit a cave witch, she shows him his terrible future being abused by Billy and Mandy.
Lord Pain, a fearsome warrior from the Plain of Eternal Suffering, appears in Billy's house looking to serve his master, Grim. However, Lord Pain is put to clean the bathroom, and is confused as to why Billy and Mandy treat Grim the way they do. Eventually, Lord Pain realizes that Mandy is to be his real master, and prepares mashed potatoes for her.
After Billy eats 19 creme-filled Atomic Frenzy Cakes he can't sleep and wants Mandy to read him a bedtime story. Then, Mandy, Billy and Grim each tell a story. For his story, Grim uses a supernatural storybook from the Underworld, which makes Billy and Mandy enter the book and reprise the tale of Hansel and Gretel. However, Billy departs from the story and follows Pinocchio who, as is later revealed, wants to devour Billy to become a real boy. Eventually, Mandy saves Billy from Pinocchio, but she and Billy remain trapped in the book as Grim, the storyteller, falls asleep.
When Billy ruins his eyes by playing too much video games and looking directly into the Sun, Mandy and Grim suggest he see an ophthalmologist. However, when Billy refuses wearing glasses or having laser surgery, Grim uses his own scythe to zap his eyes. Now, although Billy has a clean eyesight, he can also see glimpses of the future, specially horrific accidents that occur to his friends. In consequence, Grim zaps Billy's eyes multiple times to restore them to normal. In the end, Billy ends up with weird-looking eyes.
When Billy, Mandy and Grim go playing golf, they encounter boy wizard Nigel Planter again, who is there hiding from the dark wizard Lord Moldybutt (a parody of Lord Voldemort from the Harry Potter books). Then, they head back to the School of Sorcery, where they keep on running into Moldybutt, who warns them to stay away from the "Chamber Pot of Secrets" hidden in Dean Toadblatt's office. In the end, it is revealed that Lord Moldybutt is actually Toadblatt, who was disguising himself to scare off Planter. Note: This is a parody of Harry Potter and the Chamber of Secrets.
When Billy and Mandy are utterly bored, Grim takes them to Underworld's "Circus of Fear". There, the ringleader, Dr. Fear, notices Billy and Mandy, and tries to recruit them into the circus to attract customers, who would pay to see real, live humans. After they go back home, Dr. Fear captures the two kids, and Grim has to get them back. During the show, Mandy breaks free and in a strange twist of the story, she reveals that the beastmaster, Clortho, is actually Dr. Fear, who in turn is just an earthworm, leaving Billy confused.
After failing to scare a 15-year-old, the Boogieman decides to visit his old middle-school victim, Grim. Then, Grim remembers how Boogie used to be a bully, and demands an apology from him. Instead, Boogie disappears to the Underworld, taking Billy with him. Mandy and Grim follow Boogie, and to settle their differences Mandy suggest having a scaring contest, in which whoever can scare a kid the most wins. In the end, Boogie's transformation as a werewolf is not enough to scare the kid, but Grim's transformation into a giant, horrific rubber duck is.
As Billy walks into the woods to have a picnic, Yogi and a giant, feral version of Boo-Boo (from The Yogi Bear Show) come to steal his basket, and he escapes by hiding in a cave. Then, Billy is taken to the mushroom lair of the dwarves where King Beardbottom tells him the story on how the different races split the food-services industry,after the conference of Rivendell after the The Cold War,in which Ronald Reagan allows each race to chose which food to make (The meeting is a parody from the Lord of the Rings.)Then, the king sends Billy to infiltrate the elves' cookie factory to deactivate their force field, so the dwarves can assault the factory. Finally, after a fierce battle (censored out "for younger viewers", by a single clip of a pink koala continuously licking a eucalyptus leaf) and Billy's words, the elves and dwarves decide to work together and split the profits.
While going to a science museum, Billy and Mandy's schoolbus breaks down in the middle of the desert. Then, after digging for fossils, Billy, Mandy and Grim wander around and find an abandoned mine, where Billy is captured by a giant, mutant chicken. When Mandy and Grim go to rescue him, they find an underground laboratory from the days of the Cold War, where many mutant chickens were created. In the end, the mountain makes eruption, the chickens are roasted by lava, and the whole class obtains food so they don't have to resort to cannibalism. This episode might be a parody of Godzilla (1998) and Raptor Island.
Billy's cousin from the center of the Earth, Nergal Jr., goes to school for the first time, but he is worried that people may not like him. Soon enough, Junior becomes bullied by Sperg, with Miss Butterbean's allowance. Then, Billy suggests Junior to use his shape-shifting powers to take the form of Miss Butterbean, so Junior can help him pass a math test. Junior likes the idea, but he morphs into Miss Butterbean to get revenge on Sperg instead. In the end, Sperg is seen living in the center of the Earth as Junior's pet.
Trying to get revenge at Mandy for bossing them all the time, Billy and Grim put her in the "Mask of the Beast". Now, Mandy must be nice and friendly while wearing the mask, or else she'll become a hideous monster. Then, failing to remove the mask herself, and struggling to be kind to Billy and Grim, Mandy gradually turns into the beast. In the end, Billy and Grim ask Mandy to smile while she gives them a sponge bath, but this turns out to be too hard for Mandy, then she fully transforms into the beast and punishes them instead.
After watching a TV show, starring Captain Heifer and his Heifer Farms Brand Yoghurt, Billy asks Grim to turn him into a superhero with the power of squeaking and throwing yoghurt from his armpits. Then, with his wish granted, Billy goes to outer space to fight the Evil Empire, but the planet he visits is mostly inhabited. At home, despite being free of Billy, Grim still has to deal with Billy's equally dumb father, Harold. In the end, after Billy fills the alien planet with yoghurt, he returns home to be "normal".
After being bullied again by Sperg, Billy asks Grim to shrink him to enter Mandy's head to steal her "nerve". Then, after Billy swallows the raw nerve, a polyp-like organism, Mandy becomes a coward while Billy becomes tough and mean. Later, while Billy goes to get revenge at Sperg, Mandy enters Billy's head to recover her nerve. In the end, Mandy recovers her tough and cynical attitude without her nerve, which is successfully retrieved from Billy and banished from Endsville.
When Billy sees his father shaving, he decides having a beard is cool and buys "Hair Raiser Tonique", a hair-growing formula. Then, Grim casts a spell on the tonic to make its effects appear faster, but Billy exaggerates in the quantity and grows hair in all his body. Consequently, Billy is mistaken for the Sasquatch, and a reward is offered for his capture. In the end, Hoss Delgado also receives the tonic and is captured and exhibited as the Sasquatch, while Mandy collects the reward.
During a thunderstorm, a lightning hits Grim's scythe, transporting Billy to Asgard, land of the Norse gods. Then, Mandy and Grim go searching for him, while a viking wearing Billy's shirt remains at his house as a substitute. In Asgard, Billy learns about the endless battle in Valhalla, in which if a warrior dies, he is resurrected to continue fighting. In the end, Billy is surprisingly good at killing other Vikings, so Mandy and Grim are unable to convince him to return home.
When Billy forgets to do his history homework, Grim gives him a universal remote control to alter time and space so he can go back in time and finish his report. Then, Billy and Mandy travel to the American Revolution, to prehistoric times, and even to the future, where they meet an aged Billy who is just finishing the report. After a struggle for the remote, Billy ends up again in the Prehistory and the remote breaks. Fast forward into the present, every person is dumb like he is and shares his characteristic big nose, including Mandy and Irwin.
After being impressed by Irwin's realistic armor at the medieval fair, Billy wishes for a fancy armor too. Then, Grim gives him the "Cursed Suit of the Black Knight". However, when Billy needs to go to the bathroom, the curse is revealed to be that the armor can't be taken off until the person wearing it beats someone in a competition. Therefore, Billy desperately tries to defeat other people at various contests but fails to come out victorious. In the end, Billy defeats Mandy at a breakdance contest, in which Mandy decided not to participate, but he doesn't need to go to the bathroom anymore.
Grim is annoyed by Billy who thinks that a shadow is following him. Subsequently, Grim takes Billy and Mandy to the Shadows' World, where their opposites live. Grim tells them to do whatever they want, but to be back at 5 o'clock, when the portal to the normal world opens. Grim also warns Billy about the door to other dimensions, but Billy opens it and a multitude of Billys come out an wreak havoc.
Thinking that the world is chaotic enough as it is, Eris, the goddess of chaos, decides to quit chaos to work at a hamburger restaurant. Then, she entrusts Grim the Apple of Discord to watch over for her, which he seals in his old trunk. However, the apple frees itself from the chest and goes to Billy. Later, Mandy is attracted by the apple's powers, and after being persuaded by Billy's talking burrito, Billy, Mandy and Grim battle for control of the apple, which divides in three pieces. In the end, the battle results in them being fused together into an amorphous mass, and, with an evil grin on her face, Eris decides to offer the apple to Irwin too. This episode is unusual in some aspects: it starts being called Billy gets Dumber, but then the Apple of Discord swallows the screen and the real title Complete and Utter Chaos is shown instead; the episode starts at the end, and the story is told as a flashback; the talking burrito is featured prominently, but other than a brief mention, its origin is not explained.
After Billy wakes up from another nightmare involving clowns, he is more terrified than ever towards them, so Mandy and Grim try to cure him of this clown-a-phobia. First, Mandy asks Grim to bring to life a clown's head made on paper mache to entertain Billy, but the spell apparently doesn't work. Then, they dress up as clowns in an attempt to look harmless. However, after consulting with his imaginary "Inner Frat Boy", Billy changes his feeling from being afraid to being angry at clowns, and attacks them with Grim's scythe. In the end, Billy is apparently cured of his fear, but then the paper mache clown attacks and eats them.
When Billy and Mandy have a brief fight, Billy says he never wants to speak to Mandy again. The next day, Billy is over his grudge, but Mandy has already decided to find a replacement for him. Later, Mandy introduces Bobby, the new "Billy", who turns out to be a better friend than Billy, even gaining the affection of his parents, but who also wants to take over Billy's life. In the end, a jealous Billy uses Grim's scythe to open a portal and send Bobby to another dimension.
When a doctor is unable to cure Sperg of his severe case of acne, Sperg goes to see a fortune teller that deals with skin problems. Then, following a Burmese recipe in her book, the psychic tells Sperg to get the Grim Reaper's bones and rub them upon his face. In consequence, Sperg has to tolerate being friends with Billy and Grim to get access to the latter's bones. In the end, one of Grim's arms gets into a stew and when Sperg is immersed in it, the mix cures completely his acne, but it also erases his nose and mouth.
When Billy has a loose tooth he can't wait for the Tooth Fairy to appear to give him money. Then, Mandy, who doesn't believe in the Tooth Fairy, asks Sperg to end Billy's waiting by knocking his tooth off. However, Sperg's punch leaves Billy unconscious, who then has a dream about being in the wild west, where the Tooth Fairy has taken his tooth. Then, Mandy challenges the Tooth Fairy to a showdown to recover the tooth, and she comes out victorious just as Billy awakens. In the end, Billy does find money under his pillow, while the aged Tooth Fairy watches through the window.
While reading an Underworld comic book, Billy finds an advertisement for "Chocolate Sailors", a delicious chocolate candy. Billy then becomes a seller of Chocolate Sailors, but ends up eating them all by himself. The enchanted candies turn him into solid chocolate, and now Billy can't stop eating himself. Then, Billy, Mandy and Grim go searching for the Chocolate Sailor to retrieve the antidote before Billy eats himself completely. In the end, Billy eats the antidote along with other enchanted chocolates and, his head (it was all that was left of him) explodes as a result.
When Billy hangs out at Irwin's house, he finds a living mummy in the bathroom. Seeing as Irwin gets nervous, and as Billy has never met Irwin's mother, he suspects she is the mummy. Then, to scare him off, Irwin's dad tells Billy he has the "curse of the mummy". Subsequently, Billy is attacked by insects and snakes while he tries to find out the truth about the mummy. In the end, it is confirmed that Irwin's mother is in fact the mummy, but no further explanation is given as to how Irwin's family works, or how he was conceived.
Thanks to Mandy, Billy decides to get rid of his "Dinobonoid" action figures thinking he is too old for them. Subsequently, Grim makes the toys come to life, and shrinks Billy to their size so he can have a last adventure with them. Later, the "Jurassic Creeps" become aware of Grim's scythe and steal it from him to use its powers to rule the world; however, the magic that made them come alive runs out just in time, and the toys become inanimate once again. Billy reverts to his normal size too, but he stays trapped inside the box in which the action figures came.
At school, Billy, Mandy and Irwin look for a club to join. Irwin plans to join the Macrame club in order to meet girls; Billy inquires on the Junior CIA club, which forcefully recruits him; Mandy joins the "Secret Snake Club", a snake-themed club consisting of three geeks. In their headquarters, the nerds reveal that their "secret agenda" is to resurrect Shnissugah, a giant snake which lived hundreds of years ago in Canada, to take revenge against the popular kids, but they lack the power of the Underworld to do so. Then, Mandy calls for Grim, who proceeds to revive Shnissugah through the internet. In the end, Billy, as a junior agent of the CIA, stops a criminal plan by Irwin, who was using the Macrame club for personal gain; and Shnissugah turns out to be a tiny, 8-cm (3.14-in) long, harmless snake.
As Billy is tired of all the rules in his house, he can't resist the urge to try his father's new motorcycle. As expected, the motorcycle breaks down and Billy asks Grim to repair it. However, Grim's scythe turns the motorcycle it into a wild, supernatural vehicle, which in turn transforms Billy's parents and everyone else around it into undead creatures and motorized monsters. In the end, Mandy makes Billy tell the truth about breaking the motorcycle in the first place, at which point his parents and everyone else return to normal.
When Billy and Mandy's school is preparing for a big game, Mindy entrusts the care of the school's mascot, Fluffy Cat, to Billy, to protect him from being kidnapped by the rival team, the Booty Heads. Then, at Billy's house, Fluffy Cat is a disaster, so Billy's mom throws him into the basement, where the cat gets inside Grim's trunk, absorbing its powers. In the end, a giant Fluffy Cat appears just before the game wreaking havoc.
After Billy's baseball team loses badly against Mindy's, Grim decides to coach them. Mandy is not allowed on the team, as Billy is reluctant to let girls play, although he doesn't realize Mindy is a girl too. Then, Mandy puts on a baseball cap and, assuming the role of "Manfred", pitches for Billy's team anyway. With additional help from ghoulish players which played in the Underworld Little Leagues alongside Grim, Billy's team wins when Pud'n hits a home run.
While at Sassy Cat Land, the theme park dedicated to Sassy Cat (and to ridiculously long queuelines), Billy, Mandy and Grim stumble upon a closed attraction, a futuristic "house of tomorrow". Inside, they find Master Control, an intelligent computer claiming to know everything (and wishing death upon the trio when Billy angers him), and Tom Smith, a tour guide that became trapped in the house when it closed 40 years ago. Tom explains that the attraction closed when a kid, actually Billy's dad, annoyed Master Control with his dumb questions, and the robots started attacking the humans. In the end, Billy, Mandy and Grim exit the house unharmed, but Tom misses his opportunity to escape and is left behind again.
When Billy finally gets a "secret decoder ring" in his Blasto Bits cereal, he receives a holographic message from a strange creature who speaks about finding the "Secret of the Universe" in an abandoned mine shaft. Then, all the other children of Endsville, also with decoder rings, race to the mine to be the first one to get the Secret. In the end, the entire effort is revealed to be a trap laid by Lubbermouth, a worm-like creature from Grim's past, who wishes to free herself from the curse of guarding the Secret. Then, when Mindy looks down at the pit, she becomes the new guardian of the Secret and has to stay there forever.
After a trip to the mall, Mandy becomes the spokesperson for Happy Huggy Stuffy Bears, a new stuffed toy in town. After the success of her commercial, Mandy gives away stuffed bears to other children, who then start wreaking havoc in the city. As it turns out, Eris, the goddess of chaos, is behind the toys, which mind-control the children into creating chaos. In the end, Mandy decides not to share control of the world with Eris, and orders Grim to destroy the toys.
One night a strange odor travels through the city, prompting the noses of all the people, including Billy's, to follow it. The next night, Mandy, who is noseless, and Grim decide to wait outside Billy's house for the event to repeat. Then, when the odor reappears, the nose parade leads them to the shopping mall, where they meet a "Nasalmancer", a nose wizard, who is trying to take over other people's noses since he lost his own. In the end, Billy recovers his nose, but slices it in two, and gives one half to the Nasalmancer.
When Billy goes into the mud for the fifth time in the day while wearing his white tuxedo before a wedding, Grim tries to figure out why Billy is so stupid, in other words, what is his "problem". Then, Billy's dad, Harold, recounts Billy's life from his birth until he met Mandy, and explains that Billy is not dumb, but actually a genius with a certified "Honorary Genius Degree". In the end, it is quite evident to Grim that Billy's problem is his equally dumb father.
After Grim's robe comes out of the washing machine, Billy and Mandy find Thromnambular, a talking skull with ruby eyes and a number nine imprinted on his forehead. Then, Grim tells them that the skull is a magical artifact imprisoned on Earth that must grant his nine wishes in order to be free. When Mandy asks Grim why he hasn't used any of the wishes, Grim tells her that the skull will corrupt the wishes and end up affecting the wisher. Despite this, Billy runs away with the skull and makes the first wish: (1) he wishes to be in an adventure (which parodies Indiana Jones and Jonny Quest), this backfires because Irwin is eaten, which Billy complains about getting him in trouble. After this, Thromnambular is found by different people who each make a wish: (2) Billy's dad wishes he could live again his High School years, but this backfires because he is not popular; (3) General Skarr wishes to rule on high, but this backfires because he asphyxiates in space; (4) Irwin (despite being eaten already in an earlier episode) wishes he was in a Hip-hop video, but backfires because he gets punched by Mandy; (5) Pud'n wishes he had a bunny, but he is attacked by it, because "Sometimes Love Hurts"; (6) Nergal Junior wastes his wish by wishing to know what to wish for; (7) Sperg wishes for a way to get into the girls restroom, in order to bully a girl into giving him a large sack of money, this backfires because he is turned into girl, and then insulted by the other girls for being ugly; (8) Mindy wishes to be a "big star", but this backfires when she is sent into space strapped to a rocket; (9) finally, Mandy tries to auction the last wish, but Grim gets ahead and wishes the kids never found the skull in the first place. This then goes back to the beginning of the episode where Billy is staring at the washing machine, followed by Mandy pushing him into it.
When Billy gets the opportunity to adopt one of four dogs, he says he wants them all. Then, Grim uses his scythe to magically combine the dogs and create Billy's dream dog, who calls himself Wiggy Jiggy Jed. Although initially Billy and Jed are best friends, their relationship falls apart when Billy tells Jed to sleep outside. In retaliation, Jed uses the powers of Grim's trunk to build a giant machine to capture the beds of all people. In the end, Billy throws Jed a dish of primordial ooze and he dissolves.
In order to raise money to buy Sea-Critters (similar to Sea-Monkeys), Billy has a garage sale where he sells Grim's scythe to Irwin for less than two cents. Then, with the power of the scythe, Irwin hypnotizes Mandy and takes her on a date. Later, Billy and Grim try to recover the scythe, and when they do Mandy gets out of the trance. In the end, Irwin is punished by being transformed into a Sea-Critter and placed in Billy's fish bowl.
After seeing Billy, Mandy and Grim battling a strange creature, Irwin again feels rejected by Mandy. Then, Hoss Delgado, spectral exterminator, appears to help Mandy destroy the monster. Then, Delgado decides to have Irwin as his sidekick and train him to be "cool" in order win Mandy's love. In the following, Irwin gets an attire like Delgado's, and attaches an egg beater to his right hand. Then, Delgado releases a monster so Irwin can fight it and impress Mandy, but he is humiliated anyway. In the end, Mandy tells Irwin he is just a nerd, and Billy tries to assure him that being a nerd is not such a bad thing after all.
When Billy gets under his house's foundation, he encounters again his "son", Jeff the Spider, who has just laid eggs. Then, Jeff tries to make things right with Billy so he can take care of the baby spiders, as he is going to die after the eggs hatch. Naturally terrified of seeing Jeff, Billy runs away and a wild car chase ensues. In the end, the eggs hatch, and Grim decides to refill Jeff's hourglass that represents his lifetime so he doesn't die, and so he can continue to scare Billy.
After being utterly bored of watching the same movie 60 times in a row, Grim takes Billy and Mandy to "Underworld Video" where they rent "The Legend of Chupacabra". While Billy watches the tape, a small, pink chupacabra emerges from his television and Billy decides to keep it as a pet, naming it Daisy. In the end, Mandy and Grim convince Billy that he is inept in taking good care of pets, and they return the blood-sucking chupacabra to the videotape.
After Grim has a nice dream, a nightmare escapes the back of his head in the shape of a supernatural, invisible duck that makes farting noises. Then, the duck follows Grim everywhere, causing him embarrassment with the non-existent farts, and to end up in jail. Then, the duck repeats the strategy, following other citizens, including Irwin and Billy's dad, resulting in all of them going to jail too. Finally, the duck tries to annoy Mandy, but she remains imperturbable by its presence, and eventually the duck disappears and Principal Goodvibes is really super angry and gives Mandy 75 days of detention.
Billy and Mandy find a supernatural zipper from Grim's robe, and while Billy uses it to create mischief, Mandy gets herself in a sticky situation.
When Billy jumps into a supernatural puddle (a Cosmic Sinkhole, according to Grim), it takes him to the home of Granny Applecheeks, who wants to bake him into a pie. It's up to Mandy and Grim to save him, if the puddle can take them to right place.
After Grim's scythe fails to open a portal, he decides to sharpen it, but the blade breaks. Then, Billy, Mandy and Grim go to the Underworld to meet "F" (a parody of James Bond's "Q"), who is in charge of the Underworld secret gadgets. Then, "F" unveils Scythe 2.0, an autonomous computerized scythe, that Grim uses while his classic scythe is being repaired. However, when Mandy tells Grim to do his usual humiliating chores, Grim delegates the work to Scythe 2.0, which then rebels and decides to reap by itself, starting with Billy and Mandy. In the end, Grim saves the kids, takes Scythe 2.0 back to the Underworld, and returns with his old scythe.
At school, it's time for the "Presidents Fitness Test", but Billy is absolutely unfit for exercise. On the other hand, Nergal Junior uses his shape-shifting powers to become fit at will and excel in every test. Then, Billy asks Junior to transform into a pair of pants that he can wear, so he can run fast and win the 50-meter race. However, since Junior has never attempted to transform into inanimate objects he can't stop running and can't revert to his human form. In consequence, Billy keeps running forever while he becomes a national sensation known as the "Fitness Lad". However, in the end it is revealed that the story was a lie created by the narrator, who parodies The Twilight Zone.
When Billy buys a new cereal, a phoenix emerges from the box and attaches to his head, annoying everybody. Since the phoenix can't be removed because it revives every time it is destroyed, Billy, Mandy and Grim seek help by going to the factory where the cereal is produced, which is run by Eris, the goddess of chaos. In the end, Mandy tricks the phoenix into leaving Billy and attacking Eris instead. In the end, it is revealed that all the events were really an episode-within-an-episode.
When Billy desperately wants chewing gum at school, Grim gives him a bottomless gumball machine, but warns him not to swallow the gum. Naturally, Billy ignores Grim's warning and starts swallowing the gum, causing him to constantly burp bubbles that fill the entire city. Then, Mandy and Grim try to get Billy to cough the remaining gum that he has in his stomach, but instead Billy swallows the entire gumball machine. In the end, Billy coughs huge amounts of gum all over the city, and ends up with a supernatural rash.
When Billy is accepted to Mrs. Pollywinkle's dancing academy, his father tries to persuade him to forget about dancing because of his own bad experience as a child during a recital. Then, at the academy, it is revealed that Mrs. Pollywinkle is actually a powerful, dark witch set on stealing Billy's soul. Then, Billy's dad unexpectedly comes to rescue, challenging Mrs. Pollywinkle to a dance competition, which he wins using a powerful dance move. In the end, Billy's dad tells Billy to follow his dream of becoming a dancer if he so wishes, but Billy changes his mind saying that dancing is for girls.
When Grim misuses his powers to play bowling with asteroids, he is taken to the Underworld court and sentenced to 50 hours of community service. Then, at a retirement home, Billy, Mandy and Grim go to the supernatural wing, which is the Home of the Ancients, a place for retired, geriatric monsters. There, Grim meets his childhood idols, the Bride of Frankenstein, Dracula and the Wolf Man. Despite Billy's comments that the old monsters are finished, Grim sets out to prove that they are still scary. In the end, Grim tries to scare a bunch of kids in the woods, but the old monsters ruin his attempt and he walks out on them. (Grim is later put on trial for abandoning kids and the elderly out in the woods, who pleads that there is a possibility they may not have been "eaten alive by bears")
When it's scurvy-prevention day at school, Mindy parades in her float in anticipation for the Little Miss Scurvy beauty pageant, and she insults Mandy, telling her she is ugly. To prove her otherwise, and with Principal Goodvibes encouragement, Mandy considers entering the pageant. Naturally, Billy and Grim can't believe Mandy when she tells them about the idea, but finally they decide to help her. Then, Grim calls for Crabina, the Underworld's greatest makeup artist, to give Mandy a complete makeover. Crabina is shocked by Mandy's sour attitude, so she sets up principally to make her smile. At the pageant, Mandy has a real chance at winning the contest, but she still refuses to smile during her heart-warming musical number. Ultimately she smiles, but this event is so strong and powerful that it alters the natural order of things, and The Grim Adventures universe transforms into the The Powerpuff Girls universe, with Billy, Mandy and Grim turning into the three Powerpuff girls, Irwin turning into Mojo Jojo, and Professor Utonium guest starring as himself in a cameo.
When Billy's parents leave for their second honey moon, Billy is left alone at the worst possible moment, since he has invited Principal Goodvibes over to dinner so he can recommend him into Rollington Academy for the Gifted. Then, Billy's dad suggest Billy to use Eris, the goddess of chaos, and Hoss Delgado, spectral exterminator, as his substitute parents during the dinner. Naturally, the dinner is a disaster with Delgado terrorizing Goodvibes, and Eris unleashing giant alien zombie lobsters. In the end, Goodvibes forcefully recommends Billy into Rollington Academy which, as it turns out, is actually a military school.
When Billy's parents are attacked by an anaconda, Billy suggest visiting boy wizard Nigel Planter (a parody of Harry Potter), because he can talk to snakes. However, Planter in fact doesn't speak to snakes, but to snacks, and instead he asks for Billy, Mandy and Grim's help to win the affections of Huffefnie Pfefferpfeffer, a beautiful witch in the School of Sorcery (and having a striking resemblance to Gladys). Then, Planter tries using a love potion and enchanted chocolates, but they don't work. In the end, the guys have forgotten completely about Billy's parents.
When Billy's mom, Gladys, discovers crow's feet on her face, she panics and doesn't want to leave the bathroom. As Grim needs to use the bathroom, he uses his scythe to make Gladys a young girl again, thus without wrinkles. Then, Gladys goes to see Billy, but neither he nor Mandy nor Irwin recognize her, and instead, Billy calls her "Corn", because of the white bread she gave him. Then, when Corn tells Billy to do his homework, Mandy tells him to go to the movie theater instead. In consequence, Corn and Mandy struggle over who gets to control Billy. In the end, Billy's father, Harold, plays with Grim's scythe and also becomes a child; he then goes to the movies and gets together with Gladys (Corn) again.
When Billy, Mandy and Grim notice things have been disappearing in the house, they set out to investigate using a supernatural detector. They find the culprit is a talking "taking tree" in Billy's yard, who has been stealing objects since Billy's dad was a child. In order to make the tree happy, Mandy and Grim set out to trade the stolen belongings for a highly-valued Mickey Munchle baseball card, which is worth eleventy million dollars. In the end, Mandy and Grim return from the baseball shop with the real Mickey Munchle. Then, the tree returns all of the stolen things, but keeps the player.
When Nergal, the fiend from the center of the Earth, goes to visit Billy's family (his in-laws) for the weekend, he ends up staying with them over a year. When Billy finally asks his uncle to leave, Nergal says he cannot return home because he is a complete failure, having lost at a board game 599 times in a row against his own family, and experiencing constant disappointment elsewhere. Then, Billy and Grim tell him to not worry about being a failure, but to embrace it. In the end, after training with Billy and Grim, Nergal returns home and he finally wins at the board game, but he also makes a crack in the ceiling and his home starts filling with lava.
When the mall's surveillance cameras capture Grim's silhouette attacking endangered owls, a naturalist named Corey Nebraska blames Grim for the attacks, while Mandy suspects Grim is sleepwalking again. Then Billy, Mandy and Nebraska follow Grim while he sleepwalks, but they realize it is actually Gladys, Billy's mom, the one attacking the owls. When discovered, Gladys reveals her hatred toward the owls as she recounts the story on how an owl ate her pet rat, Sniffles, years ago. In the end, Billy's dad reveals that he was in fact the one who ate Sniffles merely to survive until lunch time. Note: this is the only episode without a title card
As Billy desires to be "cool" like Sperg, he has an ectoplasmic manifestation coming out of his mouth. Later, the ectoplasm grows full size and turns out to be the ghost of nineteenth-century British poet Lord Byron, who tries to teach Billy to be cool, using elaborate poetry instead of bare muscles. Subsequently, Billy uses a poem to insult Sperg's mother, and Sperg challenges Billy to a duel. Then, Billy and Lord Byron fight Sperg and his gang, but are badly beaten. In the end, Byron tells Billy he has been trained in the arts of coolness, and disappears. The Schlubs: As Grim watches the entire season of My Troubled Pony TV series (parodying My Little Pony), he learns from Mandy that the show was cancelled and doesn't have an ending. Then, Grim decides to reap the "Schlubs" (a parody of The Smurfs), 100 creatures that live in Billy's yard, to melt them into gold, so he can finance the creation of the series finale. However, Grim must get past Billy and the aggressive Schlubs themselves, including the single, large female (a parody of Smurfette). In the end, after Grim thinks he got the creatures with his scythe, Mandy appears to have used all the gold herself to become rich.
As Grim watches the entire season of My Troubled Pony TV series (parodying My Little Pony), he learns from Mandy that the show was cancelled and doesn't have an ending. Then, Grim decides to reap the "Schlubs" (a parody of The Smurfs), 100 creatures that live in Billy's yard, to melt them into gold, so he can finance the creation of the series finale. However, Grim must get past Billy and the aggressive Schlubs themselves, including the single, large female (a parody of Smurfette). In the end, after Grim thinks he got the creatures with his scythe, Mandy appears to have used all the gold herself to become rich.
When Billy and Irwin start making prank calls, everybody knows that Billy is behind the calls because every telephone has a caller ID. Then, while Billy searches in Grim's trunk in the basement for something to defeat the caller ID, he finds a skull-shaped phone with no caller ID. Then, Grim warns him to not use the phone, because it is used to call the ancient demon Cthulu, whose sole appearance makes people go mad, and if awakened will cause the destruction of the world. Despite Grim's warning, Billy and Irwin use the phone anyway, and they are sucked into it by tentacles. After the commotion, Mandy and Grim go search for Billy, and they find themselves in a strange place with several other tentacled creatures. In this place, Billy and Irwin have been hired as official prank callers and steadily turn into tentacled monsters. However, their pranks actually make the people answering the phone to become monsters, so Mandy decides to confront Cthulu himself to put an end to this. In the end, Mandy tricks Cthulu into answering her cellphone, and when he is sucked into it, Mandy disconnects the call, trapping Cthulu in the telephone lines forever. However, just as Billy, Mandy, and Irwin are about to leave, Grim has destroyed the phone at the basement, and they are unable to return.
At the beach, Billy wants to dump sand on Grim for fun. Mandy told him to go swim in the ocean. While he's having fun, a whale ate Billy. Inside, he finds Pinnochio and his papa, Geppeto. Grim and Mandy had to find the whale and get Billy out of there.
Billy wants to learn how to juggle chickens. He visits the chicken juggler legend, and the background Billy's in is based on retro black-and-white cartoons. Grim and Mandy finds Billy as a retro cartoon character while juggling chickens and having fun. After Mandy yelled that she hates retro cartoons, the phonograph turns the whole world into a black-and-white cartoon from the 1920s. How will they go back to their normally modern and colorful selves again?
Billy's dad has gotten a new job. Billy and his family are going to have to move to another part of town. However, he's always lived near to Mandy, and the two of them share the Grim Reaper. By Billy's relocating, this means that they have a problem. Who gets to "keep" Grim? Should Billy be the sole "owner" of Grim, and take him with him upon moving. Or should Grim be given to Mandy, and stay with her? To resolve this, both of them take their dispute to the Underworld Court, where a jury of hideous, nightmarish creatures (including one really annoying one) will decide once and for all who is truly the "Keeper of the Reaper."
When Billy's Mom asked what Billy wants to be when he grows up, he wants to be the grim reaper. So Grim showed Billy how to be the messenger of death. When Billy saw a girl that looks like him, he becomes smittened. But this girl is trouble when Blandy actually loves Grim. Billy becomes jealous and beats the crud out of Grim. What kind of monster Blandy is anyway?
Tired of having to deal with false alarms and giving out bonus life points, Grim visits Mighty Moe. Grim gave Mighty Moe an award for staying healthy and alive longer than anyone else. Grim finds out how to end Moe's life. So he dresses up like a snack that tastes like cheese. Will he ever get Mighty Moe to eat the cheese snack?
While Billy was trying to dig his way to the Earth's core, he stumbles upon a frozen caveman. It's Fred Flintstone! Grim and Billy thawed him out of the ice. Grim wants to reap Fred's soul, but Billy wants to keep him as a friend. At school, he presented the caveman to the class. Then Fred goes crazy and kidnaps Mrs. Butterbean.
Billy and Irwin go to mystical Japan to watch large monsters battle each other. Grim decides to take Billy and Irwin to see the monsters in action. He turns Billy into a giant warrior so that he can enjoy sparring with the giant turtle monster. Mandy comes to Japan to find Grim, Billy, and Irwin causing troubles.
After getting his kite stuck in the tree, Billy, trying to take off the kite, throws many other things on the three, including Mandy. He asks Grim for a help, but Grim's powers are useless, as there is too much nature in the tree. They ask Basil the Druid for an assistance. He wants to help, but three druids are needed for the ritual, so Basil teaches Grim and Billy to the druid skills.
In order to become cool, Billy and Irwin join a football team, so they won't get bullied anymore. Meanwhile, Mandy took over Mindy's position as the new cheerleader captain.
While at Costmo, the gang finds out that everything is too orderly. After talking to Hoss Delgado about it, they discovered that's because he's dating Eris. There isn't that much chaos anymore. So it's up to them to "stop order from taking over."
Skarr was doing a lot of gardening in order to win the "Good Neighbor Award". When he spotted a weed, Skarr tries to exterminate it. He called Grim for assistance. Then Billy comes and ruins Skarr's garden with the mower. Strange glowing tendrils wrap Skarr around and gave him the powers to bring plants to life.
When a girl named Dora comes to Billy and Mandy's school, she and Mandy become instant friends. While watching Mindy and the cheerleaders, Dora tells Mandy that if she opens her lunchbox. There's something that could destroy Mindy. Since Mandy wants to destroy Mindy, she opens the lunchbox, unleashing evil demons shaped like food. It turns out that Dora is actually Pandora, and she tricked Mandy into unleashing all of the demons. Mandy, angry that Dora tricked her, stops the end of the world by sucking the demons and Dora into the lunchbox.
When Grim gets a day off at the same time when Billy visits his grandma and Mandy does her home spa treatment, he spends his time dealing with huge lawn gnomes when Skarr takes his scythe. With both Billy and Mandy busy, he ends up getting help from Mindy and Pud'n.
When Billy destroys Grim's favorite childhood toy, Fancy Jake, Grim feels devastated and wishes he had never lost the limbo game that made him become Billy and Mandy's friend. Then, a lawyer appears saying that although the game is legally binding while all parties remain on Earth, it is not if Grim leaves Earth. In consequence, Grim follows the lawyer's advice, opens a portal, and leaves. Then, with Grim travelling aboard his spaceship, the lawyer takes off his disguise and introduces himself as Morg, the Martian Grim Reaper, who is also Emperor of Mars and commands an army of martian, brain-eating zombies. Then, so Grim can get the respect he deserves, Morg convinces Grim to conquer Earth, which they do easily while enslaving and turning all the people into zombies. Next for the reapers is to use the ultimate weapon in mind control, the Braincaster, which, if powered by a dumb mind, will allow them to control all the zombies forever. Meanwhile, Billy, Mandy and Irwin, who followed Grim to Mars hidden in his bottomless trunk, look for a way to save Earth. Then, when the kids are captured, and Billy is strapped to the Braincaster, all hope seems lost; however, at the last minute Billy talks to Grim about friendship, and Grim has a change of heart and decides to help Mandy. In the end, Billy's stupid brain overpowers the Braincaster, returning all the people to normal and foiling Morg's plan, who disappears into outer space.
When Grim decides to visit again his childhood idol, the aged king of the vampires, Dracula, the latter suggest they drive to an early bird buffet, only to get lost in the scorching desert. Then, Grim and Dracula need to find their way back home while dealing with situations like meeting a creepy truck driver and being attacked by a giant scorpion. After what they have gone through, and thinking that Dracula is just a selfish, old man, Grim decides to go a separate way; however, after finding that Dracula in fact helped him by sucking out the scorpion's venom, Grim rushes to help Dracula, and they finally make it to the diner. However, in the end, it appears that Dracula left without paying the check.
As Billy sees Hoss Delgado's manliness is action again, Billy wishes to grow up to be like him, in other words, to be a hero. Then, Grim tells Billy that in older times an evident way to become a hero was to slay a dragon, so they travel to the Middle Ages so Billy can train under the supervision of the best dragon slayer, Sir Boss Del Guapo, who resembles the present time Delgado. In the end, Billy becomes friends with the dragon he was supposed to kill and spares his life, becoming the dragon's hero. Also, Del Guapo finds himself transported to the present, where he has brief encounter with Delgado.
As Billy and Mandy celebrate Father's Day, Grim becomes very depressed that he sits inside Billy's closet only listening to country rock music. Then, Grim explains that, since his own father cared more about country rock than about him, he has been living a lie, telling his father he is a famous country rock singer, and not the actual Grim Reaper. Then, Mandy arranges for Grim's dad to come visit and she tells him the truth, but still the old man doesn't believe her. Grim decides that the only way for his dad to listen to him is while performing country music. Then, at an outdoor concert, Billy, Mandy and Grim start performing a country rock song, in which eventually Grim reveals his supernatural powers. In the end, Grim's dad accepts his son is the Reaper, but still doesn't forgive him.
As Mandy returns from Billy's house, it is evident that Mandy parents are extremely afraid of their daughter and her iron fist rule over them. Unable to live in fear any longer, Mandy's parents call a nanny from a reality TV show who specializes in disciplining spoiled children. Then, Mandy and the nanny clash several times, while the nanny tries to teach Mandy's parents to show authority to control their daughter. In the end, Grim helps the nanny in her feud against Mandy by using his scythe to make Mandy's parents more resolute; however, Mandy quickly restores her control over her parents, and shows the nanny she actually controls everything and everyone.
When Mandy says even a trained monkey is more competent to do cleaning chores than Grim, and would complain less, Grim makes Dickie Galoot, a monkey appearing in a Japanese-styled animation, come to life to prove her wrong. Then, as Dickie turns out to be extremely good at cleaning Mandy's house, Grim decides to leave the kids for good; however, due to his friendship contract, Grim is unable to break free, and so he is forced to battle Dickie to recover his place as the "cleaning monkey" of the group. In the end, Grim successfully defeats Dickie at cleaning Billy's house, but this all turns out to be an ingenious plan devised by Mandy to win a bet against Billy.
At a school fair, Grim's scythe accidentally transforms the dull Principal Goodvibes and his hippopotamus into gangster rappers, Goodvibes now calling himself Principal Goodbling. In the following, Goodbling changes the entire school to be more hip-hop oriented, to the annoyance of Mandy. Although initially Grim likes the new style of the school principal, he later thinks Goodbling is just a poseur and goes to talk to him, but Goodbling attacks with yo-mama jokes. In the end, Irwin's grandmother, Tanya, confronts Goodbling and proves to be better than he is at yo-mama jokes that Goodbling reverts to being the boring Goodvibes.
As Grim appears in an Underworld TV commercial for "Big Move" laxative pills, an accompanying contest promises a day with the famous Grim Reaper to the monster who writes the best 500-word-or-less essay describing the fun things they would do. It turns out the winner of the contest, and sole participant, is the dim-witted Fred Fredburger, who only wants to eat frozen yoghurt. Also, the Big Move company blames Grim for their sales going down since they hired him. In consequence, Grim tries save his reputation and make the best day for Fred, but it is a disaster with Grim ruining Fred's yoghurt and Fred going missing in an amusement park. In the end, the Big Move executives give Grim a beating for ruining their company, and Fred finds his own paradise in a cold place with nachos- and frozen yoghurt-loving creatures.
When Billy finds his "son" Jeff the Spider lying in his bed with "Spider Pox", he goes to Mandy for help to get rid of the giant spider. While ignoring Billy, the next morning Mandy awakens afflicted by Spider Pox too, developing four additional arms and the ability to produce spider web. Later, Mandy's condition progresses and she completely turns into a giant spider, who then captures Billy's parents and Grim. Then, Grim tells Billy that, to cure Mandy, he must use the venom of the spider that infected her. In the end, while Billy successfully gives Mandy Jeff's venom, he also carried the virus and infected the people of the city, who all turned into spiders.
As Billy, Mandy, Grim, and Irwin hang from a rope about to be eaten by a giant sea serpent, Irwin wonders how they came into that trouble. Then, Billy and Grim each tell disparate stories on how they became best friends originally. Billy's fantastic story is about he and Mandy being space patrol officers who collect the Grim Reaper's bones, cloak, and skull to summon him; Grim tells a story on how the evil Mandy and his pet servant Billy managed to capture him inside a containment unit (parodying the Ghostbusters' ghost traps). In the end, Mandy quickly tells the real story, and footage from the first episode is seen, before the four are swallowed whole by the serpent.
The Crass Unicorn: There's trouble in the Enchanted Forest, and Billy finds a unicorn who is a real jerk. Billy & Mandy Begins: Billy, Mandy, and Grim each narrate a different version about how they met.
When Grim leaves the house to meet someone he met on the internet, Billy looks inside Grim's trunk for something to entertain himself. Then, Billy finds a magical talking Rubik's Cube, which releases the demon Pinface, who has bowling pins in his head (a parody of Pinhead from Hellraiser). Then, Pinface proceeds to call his minions to conquer Earth, but the minions are more interested in throwing a house party. Later, it is revealed that Grim and Pinface already know each other, and Grim even broke up with Pinface's sister. In the end, Billy's father cheats and solves the magical cube by rearranging the stickers, trapping Pinface and his minions inside it again.
As Billy behaves more reckless than ever and can't stop breaking everything in sight, Mandy thinks he should go some place where he can release all his urge to destroy until he gets tired of it. Then, Mandy, Grim and Irwin go to Level 9, home of the fearsome warrior Lord Pain, to convince him to take Billy. Meanwhile, Billy receives psychological treatment and it is revealed that his desire to destroy stems from lack of attention when he was younger. Then, Lord Pain abducts him, and together they start destroying everything in Level 9, which apparently is uninhabited. In the end, Billy is still not satisfied, so he and Lord Pain return to Endsville and carry on breaking everything.
When Billy, Mandy and Grim attend an Ancient Egypt exhibit at the museum, they meet with Irwin who explains that, as his mother is a mummy, they are visiting Irwin's grandfather, the great Pharaoh King Popen Locken. Later that night, Irwin's grandfather visits Irwin in his room and offers him the Pharaoh's crown and the possibility of building his own pyramid to attract women; Irwin accepts, calling himself King Tooten Pooten, and soon they turn the citizens into slaves to build the pyramid. In the end, against his mother's wishes, Irwin decides to finish the pyramid; however, there is something he didn't anticipate, as he, the Pharaoh, needs to remain entombed inside it.
As Billy realizes the three geeks of the Secret Snake Club get doctor's notes to avoid Physical Education (P.E.) class, he wants to know their secret to avoid the class too. Then, all the boys in the class join the club and all, except Billy, get doctor's notes from Billy's dad, who poses as a doctor. Then, while Billy is the only one exercising in the class, the Snake Club summons a snake to destroy the gym. However, since the invoked snake is tiny, Sperg uses Grim's scythe to make it a giant. In the end, Mandy and the other girls beat the boys and their snake because they did appreciate the P.E. class as an outlet for their aggression.
After watching the Unsolvable Mysteries TV show, Grim realizes he forgot a million years ago to reap the Abominable Snowman living in the Himalayas. Then, Billy, Mandy and Grim go there to finish the job and also to obtain videographic proof of the snowman's existence. The Yeti, who likes to be called Abom, manages to escape Grim several times, before finally being trapped by the moving glacier. In the end, as Grim watches the TV show again, it is apparent that he may have forgotten to reap the Loch Ness monster too.
When Billy fails an important test, the result of which will go into his permanent record, he asks Grim to magically alter his grade from an "F" to an "A"; as Grim reluctantly changes the grade, Billy becomes a genius, but reality is thrown completely off balance. Then, Mandy and Grim go back in time to stop the past Grim from helping Billy, but it doesn't work. They keep going back in time to different epochs, each time meeting another Grim, eventually trying to stop Billy's ancestors from conceiving him, but nothing works. After meeting Billy's distant dinosaur relative, the episode ends abruptly as Grim wonders what the end of this could be.
When Nergal comes to tell the guys about his new pizza joint, Grim thinks he can do better by using his Granny's recipe. Then, a pizza war ensues between Nergal's Pizza and Grim's Pizza, with each pizzeria launching TV ads and discrediting each other. Finally, Nergal Jr. uses his shape-shifting abilities to infiltrate Grim's pizza and replace Granny Grim's hot sauce with a "ghastly elixir". The result is pizzas becoming monsters and attacking the city, and the citizens developing parasites similar to Nergal. In the end, Nergal and his family leave the city just as Grim's sauce explodes.
After Billy, Mandy and Grim are disappointed with the SassyCat amusement park submarine attraction, Grim uses his powers to take them to the bottom of the ocean to have a real magical adventure. There, they are sentenced to death for trespassing into the Googen Kingdom by King Triceps, a wrestling merman. However, the king's daughter, Hariel, also a mermaid, stops the sacrifice and tries to marry Billy in order to inherit the kingdom. Then, it is revealed that King Triceps is actually Hariel's sister, the sea witch Uvula, who also tries inherit the kingdom. A cat fight ensues between the two ladies, which ends when Billy agrees to marry both of them. Then, the plot is eventually revealed to be a story Billy is telling to Miss Butterbean, who initially asked him what happened to his report.
As General Skarr is once again annoyed by Billy, Hector Con Carne and Major Dr. Ghastly arrive in his house with the intention of luring him back to the recently relaunched Evil Con Carne world domination organization. Although initially refusing to rejoin, Skarr later accepts with the condition that Billy and the other neighbors be destroyed. After a few weeks of living together and preparations, Evil Con Carne's ultimate weapon is revealed to be an army of tanks that shoot giant rubber bands. In the end, Skarr's all-out attack over the neighborhood is foiled when Billy tricks Hector into shooting Skarr's garden and they get into a fight. Special Guest Stars: Phil LaMarr as Hector Con Carne, Frank Welker as Boskov, Grey DeLisle as Major Dr. Gastly Note: This is a crossover episode with the series Evil Con Carne
As General Skarr has trouble finding a job, the recruiter tells him to attend anger management classes if he wants to work again. Then, Skarr finds out Mandy and Grim are attending too, Mandy for staring at the school monitor, and Grim for enjoying too much his job. The instructor of the class, Larry, turns out to be a peace-loving, short man riding a tricycle, who teaches the trio ways to calm down when angered, including counting to ten, and using harmless weapons to let go of their anger. In the end, Larry invites Billy to the class, and Mandy, Grim, and Skarr all manage to contain themselves; however, Larry himself suffers an episode of rage over a parking space and he is arrested.
When Mandy finds Billy playing with Grim's gigantic dog, Cerberus, she tells Grim to keep Billy under tight control because she needs a good night of sleep to be ready for the next day's test. Then, with a little persuasion from his own dad, Billy tries to wake up Mandy at night, so she will fail the test and he can score higher than her for the first time. After Grim spends the night guarding Mandy's house from Billy, the latter apparently succeeds in waking up Mandy. However, it is revealed that this Mandy is in fact Irwin, used as a decoy by the real Mandy, who slept in her dog's house. In the end, Mandy passes the test, and Grim is punished for not guarding her properly.
When Billy, Mandy and Grim once again go to the beach, Grim warns Billy to avoid swimming too far, because the "undertoad", a frog-like creature, will try to drag him into the sea. Naturally, Billy encounters the undertoad, and he barely makes it back to the beach. Then, with the dangers of the sea averted, the guys go back home, but the undertoad is set on bringing Billy down, that he follows him to his house. The next day, the undertoad becomes a constant annoyance to Billy, even at school. In the end, Grim and Mandy capture the undertoad, and set sail to release him at sea, where they meat the giant Mama undertoad.
A scene of Endsville two weeks into the future shows a dystopian world ruled by the "Lord of Horror", who wields the all-powerful artifact known as "Horror's Hand". At the same time, two robotic replicas of Billy and Mandy are sent into the past, to stop the real Billy and Mandy from interfering with the current events. In the present, Grim goes to reap General Skarr, who accidentally got a big wound in his torso. However, due to Billy and Mandy's meddling, Skarr escapes, and they make a big mess in the city. Following his failure to be an effective Reaper, Grim is taken to the Underworld Court, presided by Judge Roy Spleen, where he is sued for misuse of his powers by his nemesis, the Boogeyman. After the trial, Grim is found guilty, is stripped of his rank and magical scythe, and he, Billy, Mandy, and Irwin are sentenced to be exiled. Then, Boogey volunteers to carry on the sentence by taking the prisoners aboard his ship, and dropping them off in a river of fire; he plans to do this while he sails to obtain Horror's Hand, an object capable of transforming him into the scariest and most powerful being in existence. The group of Billy, Mandy, Irwin, and the powerless Grim, escapes from Boogey's ship, and set themselves to reach Horror's Hand before Boogey does. They eventually meet Horror, the guardian of the Hand, at the same time Boogey and his crew arrive. Then, in order to decide who will have the honour to battle Horror for his Hand, the heroes and Boogey participate in a challenging obstacle course, which the heroes win against all odds. After dispatching Horror with ease, Billy, Mandy and Irwin reach for the Hand, but it defends itself by making their worst nightmares come to life. Then, Boogey gets ahold of Horror's Hand, but he turns out to be the least scaring creature ever, seriously injuring himself, and being abandoned by his own crew. Then, Grim recovers Horror's Hand, and at the same time his sentence is revoked, becoming the Reaper once again
When Billy accidentally food-poisons Miss Butterbean, Principal Goodvibes offers Grim the job of substitute teacher, which Grim accepts as now Billy and Mandy have to obey him. In the following, Grim sends misbehaving students to the "Detention Dimension", a place of eternal classroom punishment, until only Mandy remains in his class. Then, Grim tricks Mandy into opening a portal and she is dragged into the dimension too. In the end, Mandy proves to be more terrifying than Miss Slither, the giant, rattlesnake-like creature in charge of the Detention Dimension, that Mandy escapes the place and takes revenge on Grim by sending him there too.
A scene of Endsville two weeks into the future shows a dystopian world ruled by the "Lord of Horror", who wields the all-powerful artifact known as "Horror's Hand". At the same time, two robotic replicas of Billy and Mandy are sent into the past, to stop the real Billy and Mandy from interfering with the current events. In the present, Grim goes to reap General Skarr, who accidentally got a big wound in his torso. However, due to Billy and Mandy's meddling, Skarr escapes, and they make a big mess in the city. Following his failure to be an effective Reaper, Grim is taken to the Underworld Court, presided by Judge Roy Spleen, where he is sued for misuse of his powers by his nemesis, the Boogeyman. After the trial, Grim is found guilty, is stripped of his rank and magical scythe, and he, Billy, Mandy, and Irwin are sentenced to be exiled. Then, Boogey volunteers to carry on the sentence by taking the prisoners aboard his ship, and dropping them off in a river of fire; he plans to do this while he sails to obtain Horror's Hand, an object capable of transforming him into the scariest and most powerful being in existence. The group of Billy, Mandy, Irwin, and the powerless Grim, escapes from Boogey's ship, and set themselves to reach Horror's Hand before Boogey does. They eventually meet Horror, the guardian of the Hand, at the same time Boogey and his crew arrive. Then, in order to decide who will have the honour to battle Horror for his Hand, the heroes and Boogey participate in a challenging obstacle course, which the heroes win against all odds. After dispatching Horror with ease, Billy, Mandy and Irwin reach for the Hand, but it defends itself by making their worst nightmares come to life. Then, Boogey gets ahold of Horror's Hand, but he turns out to be the least scaring creature ever, seriously injuring himself, and being abandoned by his own crew. Then, Grim recovers Horror's Hand, and at the same time his sentence is revoked, becoming the Reaper once again
When Irwin lacks the courage to ask Mandy to go with him to the Valentine's Day school dance, he tells Nergal Jr. to do it for him. Then, Mandy mistakes Junior's invitation for his own, and surprisingly accepts to go with him, which naturally makes Irwin jealous. Then, with the ill advice received from his father, to be possessive with Mandy, at the dance Junior becomes overprotective of her, that eventually he and Irwin start fighting, throwing punch at each other and ruining the ball. In the end, it is revealed that this was Mandy's true intention all along so that no one could enjoy Valentine's Day.
When Billy is sent to bed after playing with his Dr. Brainiac action figure, he wishes he had an adventure. Then, he notices a strange light outside and wanders into a corn field to investigate; there, he encounters Sperg, and they are both abducted by aliens who experiment with them. Later, when they return home, it is revealed that Sperg has a bomb implanted in his head, and also that there is a shortage of dairy products; Billy explains that the aliens are stealing Earth's dairy products because they are werewolf-like creatures who need cheese, and they have already mined all the cheese in the Moon. In the following, Billy's crazy story is confirmed when too many UFOs appear. Then, Billy says they must assemble a team of diary superheroes, the Green Squeaker (Billy), Milk Mandy, the Cheese Reaper, and Diary Boy (Sperg), to combat the aliens, but everybody is opposed to the idea. Later, the four of them have been captured and are sent to the Moon to be destroyed, but they escape and try to stop the Moon ship from getting to Earth. At that time, the Moon aliens start their transformation into werewolves, and they bite Billy, who becomes a werewolf too. With their backs to the wall, Grim finally chooses to give Billy, Mandy and himself their dairy superpowers. Meanwhile, Sperg sacrifices himself by letting the bomb in his head explode in the control room, thus crashing the spaceship in the Moon and saving Earth. A final segment shows what happened to Billy, Mandy, Grim, Sperg, Dr. Brainiac, and even the Moon people, that remain attempting to destroy the humans by extracting their brains to steal their knowledge after they discussed and revealed their master plan to escape with Endsville's supply of cheese while showing images of the characters from the other shows in the the crossover Cartoon Network Invaded which meant that they were the masterminds behind the entire event.This was the fifth and final chapter of Cartoon Network Invaded which also concluded with an
On a rainy day, several giant spiders appear in Billy and Mandy's school and start kidnapping the children one by one. Grim presumes this is somehow related to his past, but doesn't figure it out until he receives a message saying that Velma, the Spider Queen, an old friend from high school, is responsible for it. Meanwhile, Billy meets with his "son", Jeff the Spider, who informs him that he is precisely marrying Velma. After trying to recover a talking carton of chocolate milk from Jeff, Billy and Jeff get into a fight, and Jeff looks angrier than ever before. Upon meeting in the school's football field, Velma tells Grim that she has finally come to devour his skull and absorb his powers, since one hundred thousand years ago Grim cheated and robbed her from the possibility of becoming the Reaper. Converting the school into her own palace, and with help from the Dark Elves, Velma captures Mandy, Mindy, and Grim, and proceeds to devour the latter's skull. However, when Velma cracks open Grim's skull, his thoughts start coming out, and she is able to see his memories. In the following, Grim's skull is connected to a screen, and the story on how he became the Reaper is shown. It is revealed that an election was held in the Underworld's high school to choose the Reaper, in which students had to vote on the scariest participant. Velma was the scariest contester and she was getting most of the votes over the pathetic Grim and the Boogeyman. Then, Boogey decided to tamper with the ballots, and Grim in turn decided to help Velma, but she got the impression that Grim was the cheater and ran away. Then, in a fit of anger, Grim used the prototype scythe in a spectacular fashion to scare Boogey off. In consequence, the people that hadn't yet cast their vote, voted for Grim, who thus became the new Reaper. While the story is being told, Mandy and Mindy form a temporary alliance to fight the spiders, and also Billy reconciles with Jeff, and fights the spider-cow centaur-li
As Billy, Mandy, and Irwin need to write a school report on tall tales, Grim tells outrageous tall tales about Pecos Billy (based on Pecos Bill), Paula Bunyan (based on Paul Bunyan), and John Henry. In Grim's stories, Pecos Billy (Billy) tames a twister using his personal laser-shooting cow-like spacecraft, saving an Arizona trailer park; Paula Bunyan (Mandy) uses her blue ox companion, Babe, to stomp over a villain, creating the Grand Canyon in the process; John Henry (Irwin) digs through a tunnel so fast that he breaks the laws of Physics and bursts into the "8th dimension". After Grim tells them the stories, Mandy informs Billy and Irwin that he is trying to get them F's.
On a rainy day, several giant spiders appear in Billy and Mandy's school and start kidnapping the children one by one. Grim presumes this is somehow related to his past, but doesn't figure it out until he receives a message saying that Velma, the Spider Queen, an old friend from high school, is responsible for it. Meanwhile, Billy meets with his "son", Jeff the Spider, who informs him that he is precisely marrying Velma. After trying to recover a talking carton of chocolate milk from Jeff, Billy and Jeff get into a fight, and Jeff looks angrier than ever before. Upon meeting in the school's football field, Velma tells Grim that she has finally come to devour his skull and absorb his powers, since one hundred thousand years ago Grim cheated and robbed her from the possibility of becoming the Reaper. Converting the school into her own palace, and with help from the Dark Elves, Velma captures Mandy, Mindy, and Grim, and proceeds to devour the latter's skull. However, when Velma cracks open Grim's skull, his thoughts start coming out, and she is able to see his memories. In the following, Grim's skull is connected to a screen, and the story on how he became the Reaper is shown. It is revealed that an election was held in the Underworld's high school to choose the Reaper, in which students had to vote on the scariest participant. Velma was the scariest contester and she was getting most of the votes over the pathetic Grim and the Boogeyman. Then, Boogey decided to tamper with the ballots, and Grim in turn decided to help Velma, but she got the impression that Grim was the cheater and ran away. Then, in a fit of anger, Grim used the prototype scythe in a spectacular fashion to scare Boogey off. In consequence, the people that hadn't yet cast their vote, voted for Grim, who thus became the new Reaper. While the story is being told, Mandy and Mindy form a temporary alliance to fight the spiders, and also Billy reconciles with Jeff, and fights the spider-cow centaur-li
When vampire hunter Lionel Van Helsing prepares to kill Dracula, Billy, Mandy and Grim arrive to stop him, since, after all, Dracula is just senile and harmless. Then, Van Helsing reveals the source of his hatred: in the past, he and Dracula were "best friends forever", until Dracula used his irresistible dance moves to marry Tanya, the woman of his dreams. Later, Tanya arrives too, revealing that she is none other than Irwin's grandmother, making Irwin half-vampire on his father's side, and half-mummy on his mother's side. In the end, Van Helsing leaves, but Dracula is unsatisfied with his newfound family of nerds.
When Billy, Mandy and Grim go to a joke shop, they find the owner is former boy wizard Nigel Planter (a parody of Harry Potter), who reveals that his powers diminished and was kicked out of Toadblatt's School of Sorcery. Then, Planter steals Grim's scythe and heads to the school to exact revenge on those who wronged him. In the following, the guys seek the help of Planter's sworn enemy, Lord Moldybutt (a parody of Lord Voldemort), to find the school. In the end, Grim recovers his scythe, and Moldybutt turns out to be in fact only a real estate agent, who informs Planter that he is the heir to the "Peanuts by Planter" farming company.
When Grim can't take any more abuse from Mandy, Billy tries using Grim's scythe to shrink her to mouse size. However, instead of shrinking, Mandy becomes a giant and destroys Billy's house. Although Mandy enjoys being a giant for a while, there are inconveniences, as she keeps growing as time passes, and she wants to return to her normal size. However, Billy is the only one who can cancel the curse he put on Mandy, and he refuses to do so. In the end, Mandy grows bigger than the planet, and she finds herself in the "Realm of the Infinite" with other creatures that, like her, grow at infinite pace. Naturally, Mandy starts bossing them around to please her.
When Billy's dad drives Billy, Mandy and Grim to the hamburger restaurant, they somehow end up in Mexico. There, the people are celebrating Dia de los Muertos, but local kids say it may be the last celebration ever, because Del Uglio, a masked and ugly luchador, is set on stealing the "Golden Nose of Chipotle", a prehispanic relic on which the festivity is based. To get to the nose, Del Uglio has one half of the map, while the other half is held by his lost twin brother, who turns out to be Billy. In the end, Grim defeats Del Uglio, but it is Mandy who keeps the golden nose for herself, which makes her rich.
When Billy starts taking pictures with a camera found in Grim's trunk, Grim tells him that is an Underworld's True-heart Camera, which shows the real essence of a person's heart. Then, when Mandy takes Irwin's picture, it is revealed that he is actually half-good and half-evil. Irwin explains that although he was born evil, his dad taught him about love and respect, and he had a change of heart. Upon knowing this, and against her own wishes, Mandy also experiences a painful change, turning good. Finally, Mandy and Irwin kiss. However, this kiss makes Mandy revert to her old dark self, which was Irwin's true intention, as he likes her just the way she is.
Billy, Irwin and Mandy go trick-or-treating on Halloween, and an evil marshmallow bunny attacks children with chocolate beasts.
While Billy's Dad is underwear shopping, Billy wears his dad's lucky pants, and accidentely rips them with Grim's scythe. He calls Ed, Edd n Eddy, and they recommend Kids Next Door for charity. Numbah 1 disguises as Billy while Billy is taken back to the Deep Sea Lab. Mandy arrives at Billy's house and knows Numbah 1 is not Billy, and tortures him into revealing the truth. Meanwhile, the Delightful Children From Down the Lane and Billy accidentely fuse with the scythes power to create the Delightful Reaper. Mandy takes over the KND by fooling Numbah 363 and the rest of the KND, but Numbah 5 knows she's not Numabh 1, but is taken to the med lab. The Delightful Reaper assimilates nearly all of Endsville (including Numbah 2) and grows more powerful. Numbah 1 and Grim try to get the KND to see sense but are imprisoned. Numbah 5 escapes and finds Numbah 1 and Grim. Grim and Numbah 1 fuse with the Bone of Barnacles and become the Skeleton Samurai. Mandy in her Mandrobot (Monkeys And Nice Doggies Relax On Bellies Of Turtles) fight the Delightful Reaper, and so does the Skeleton Samurai, but they cannot defeat it. Grim finds out that the pants are Billy's Dads pants (which we now find out are immune to lasers, supernatural energies and mustard). Mandy is their only hope to defeat the Reaper, but instead they fuse with the Reaper. Billy's Dad takes off the pants, they destroy the Reaper, and all the kids return.
Billy looks into Grim's trunk and sees a monster and names it Myron. But when Billy brings Myron outside to his backyard, he gets eaten in the end.
In 2007, Cartoon Network released a short based off of The Grim Adventures of Billy & Mandy titled Matinee Mandy. It is unknown as to what specific date the short was released or if it even aired in America at all. Two versions of the short are known to exist online, both uploaded to YouTube, but neither is in English. The first upload is in 4:3 and features both Chinese subtitles and Chinese voices. The second upload is in widescreen; it appears to be a partial recording from a Thai version of Boomerang and features Thai dubbing. It is unknown if the English version was ever released or if any copies of it still exist. In May of 2017, YouTube user shooterboss uploaded the Chinese dub with fan-made English subtitles.
Billy, Mandy and Grim try to save Christmas when vampires invade Santa's workshop in the North Pole.
