When Mac, a shy 8-year-old boy, is forced to give up his imaginary friend, Bloo, he finds the perfect place for him: Foster's Home for Imaginary Friends. There, they meet many of the home's residents, like Eduardo, Wilt and Coco; as well as the home's staff. Their problems appear to be solved until it is revealed that Foster's is an foster home and adoption center, and, if Mac isn't there at the time someone tries, another person could adopt Bloo. To make matters worse, a sinister plot by the evil imaginary friend Duchess, uses Mac's 13-year-old bully brother, Terrence, and puts Bloo in peril. Now Mac and his new friends from Foster's must work together to save Mac's best buddy Bloo.
When Mac, a shy 8-year-old boy, is forced to give up his Imaginary Friend, Bloo, he finds the perfect place for him: Foster's Home for Imaginary Friends. There, they meet many of the home's residents, like Eduardo, Wilt and Coco; as well as the home's staff. Their problems appear to be solved until it is revealed that Foster's is an adoption center, and, if Mac isn't there at the time someone tries, they could adopt Bloo. To make matters worse, a sinister plot by an evil Imaginary Friend uses Mac's 13-year-old bully brother, Terrence, and puts Bloo in peril. Now Mac and his new friends from Foster's must work together to save Mac's best buddy Bloo.
Mr. Herriman isn't happy about Bloo being able to stay at the home indefinitely, and is getting on the little guy's case about the rules of the house. Unfortunately, when Bloo learns that Mr. Herriman will have him ejected from the home if he doesn't toe the line, Bloo gets so stressed out that he accidentally breaks a statue of Madame Foster! Bloo and his buddies will have to fix the "busted bust" before Mr. Herriman finds out and has Bloo thrown out on the street.
When Mac visits Foster's, Bloo wants to show him something up on the roof, though when it's time for them to go back downstairs, they find themselves lost and unable to get downstairs. With Bloo becoming unstable due to hunger and Mac potentially getting in more and more trouble with each passing minute, will they manage to find their way back down before it's too late?
It's Adopt-A-Thought Saturday, an event that focuses on getting good friends adopted on the weekends when children are out of school. But Mac and Bloo find out after their good friend Jokey gets adopted. While the event is usually a good thing for both imaginary friends and those seeking to adopt them, Bloo doesn't want his friends to be adopted, so he works with Mac to try to find a way to put an end to the event. From atracting friends in the house with scented cupcakes to dropping plastic spiders, they try as many plans as they can. Will they be successful in prevent the adoption of their friends, or are their best efforts in vain?
It's Madame Foster's birthday and Frankie has forgotten the one thing necessary for any party, the streamers! As Mr. Herriman orders her to go get some, Bloo, Eduardo, Mac, Wilt, and Coco tag along as well. They have five minutes left until they can leave, so they stop a one store and Frankie falls asleep in a vibrating chair and when she wakes up, everyone left to different places. Will Frankie be able to get to the party in time?
Bloo and Mac enjoy playing with each other in the mud while raining, but sometimes there can be consequences. As Mac and Bloo get sick, causing Bloo to turn white and Frankie to take Mac home, Bloo misses out on the scary movie the friends planned to watch that night. However, the movie scares the friends enough that they believe that the ghost is real, and they mistake Bloo to be the ghost. Will they be able to figure out it's him before they end up hurting Bloo or themselves in the process?
Bloo finds out about a door in the home that everyone is forbidden to open. As he asks around about the door, no one tells him what is inside of it. However, in the middle of the night, Bloo manages to sneak to the door and open it, but will he like what he has found or will his deeds cause untold trouble?
Terrence has an idea to make up a friend named Red to beat Bloo and Mac up with, though the friend he creates doesn't seem to be capable of comprehending the task it was given. Will Red serve Terrence as he was created for, or will it choose it's own path and disregard what Terrence ordered him to do?
Bloo is jealous of Wilt getting special attention for the number of abandoned imaginary friends he brings to Foster's, so he tries to rescue imaginary friends just like Wilt does. When Bloo finds a man in a cell-phone suit and thinks he is a friend, he takes him to Foster's, thinking everyone will give him more praise than they give Wilt.
Mac and Bloo are using Frankie's digital camera to make video interviews for the new Foster's website, when they stumble upon Mr. Herriman indulging Madame Foster's whims and doing a little dance for her. Much to Mac's chagrin, not only do Bloo and Frankie show the embarrassing footage to almost everyone in the house, but Bloo uploads the film to the Internet. It won't be long before Mr. Herriman discovers he's become the latest Internet fad, and you can bet he won't be happy!
As a new day begins at Foster's, with everyone enjoying their favorite television program, The Loved and the Loveless, a new friend named Berry enters the house as sweet as can be, though with one glance on Bloo became love struck and determined to make Bloo love her back, though there is one thing that truthfully stands between her and Bloo, and that is Mac. When Mac and Bloo are trying to win a world record, Berry gets mad. After many schemes to try to get rid of Mac, Berry tries to tell Bloo that Mac is stopping him from winning the world record. When Bloo says that to Mac, he gets mad and dosen't want to break a world record anymore. But Berry makes Bloo the almost world's largest rubber band ball and both of them will put the last rubber band to make it the biggest. Meanwhile, Mac is running to Foster's so Bloo and Mac can put on the last rubber band, but will Mac get there in time before Berry and Bloo put on the rubber band?
After Eduardo finds a puppy when he was taking out the trash, he decides to keep it, despite the fact that dogs are not permitted inside the house. However, despite Eduardo's best efforts, the dog gets loose and starts causing problems that Eduardo takes the blame for in fear of the puppy being found out. Will Eduardo manage to keep the puppy without Mr. Herriman finding out, or will the puppy be forced to leave due to Mr. Herriman's strict policy against dogs?
Mac drafts the gang onto Madame Foster's bowling team to help her beat her arch-rival, Jerkhins. But when Mac gets booted off his own team, he must learn the ways of the ball from a bowling guru. Meanwhile, Bloo is the best player on Foster's team, but the other team steals him by offering him a paddleball if he wins for their team. When Mac is done with his bowling lessons by the bowling guru, he comes back to Foster's team. Will Mac be good enough to beat the other team which now has Bloo or will he mess up and lose?
Where There's a Wilt There's a Way: All Wilt wants to do is watch his favorite basketball game on TV, but the house's ridiculous requests and Wilt's ridiculous inability to refuse them threaten to keep him from the big game.
A new imaginary friend has come to Foster's, but he keeps misbehaving all around the house. All other imaginary friends are taking the blame. That is, until Bloo comes up with his master plan!
Frankie and Madame Foster are leaving for a while, so Mr. Herriman is placed in charge of the house. However, Madame Foster inadvertently gives Bloo the idea to throw a wild party, and he plans to do so without Mr. Herriman's consent. While they manage to come up with a method to distract Mr. Herriman, there is still one person that could stop the party, and that's Mac, though Bloo knows that with a little bit of sugar, Mac can be placed under control, or so he thinks.
Mac takes Bloo to school for show and tell. The kids love Bloo so much, that they imagine Bloos themselves. Tons of Bloos are created, and Bloo dubs them his brothers and himself leader, but will Bloo take it too far?
When Ivan, a seeing eye friend, loses his blind kid, the friends try to find the boy before harm comes to the seeing eye's creator.
When Foster's needs a new roof, Bloo bakes up a plan to sell Madame Foster's amazing cookies after his first attempt at selling lemonaid int he middle of winter failed. When they finally get enough money to buy a new roof, Bloo gets a "little" carried away and wants to become rich and make all the imaginary friends his servants! Will Bloo's business plan work, or will his treatment of the friends make his sweet success turn sour?
Mac develops a crush on Frankie when she said that she loved him for doing her paper work and kisses him. Later, Bloo develops a crush on Frankie too and Mac and Bloo compete for her love. But when Frankie suddenly starts professing her love for an unnamed suitor, Mac and Bloo become jealous and try to thwart every guy she comes in contact with, namely Chris (a pizza guy), Prince Charming (an imaginary friend), and her real date, Dylan who takes her to a fancy restraunt for their date. Will Bloo, Mac, Chris, and Prince Charming win her love?
One morning, Mac wakes up to find that he's unintentionally created another imaginary friend named Cheese. Madame Foster allows the same rules as there are for Bloo, but Bloo does not approve of his new brother. After many attempts to get rid of him, Cheese disappears on his own. Bloo realizes that Foster's could be a very dangerous place for one so stupid as Cheese. Can he find him before something happens or Mac notices Cheese is missing?
The gang goes an arcade and everyone's winning lots of tickets except Bloo. Bloo then becomes very interested in a prize that's 500 tickets: glow in the dark Dracula teeth. So Bloo wants them to give them their tickets so he can get one, but the others decided to collect all of their tickets and get a rubber elephant, which Bloo grows an obsession with later on. But when Frankie, who's holding the rubber elephant, goes to sleep, Bloo sneaks in and steals it. When he's playing with, it breaks. The only option is to go to the arcade and win 500 tickets to get another rubber elephant. Can he get the elephant before the others find out?
Bloo has a reputation for being a funny imaginary friend, though his jokes sometimes offend people. When Bloo cracks a joke about a new imaginary friend's height, the new guy challenges him to meet him outside at 4 o'clock. Will Bloo manage to find a way to dodge the challenge or will he have to face the consequences of his joke and possibly be severely injured?
When Bloo becomes jealous of Eduardo and the other friends for appearing on TV, he pretends to be a very sick friend in order to appear, despite the fact that it is only for friends up for adoption. A Hollywood agent named Kip Snip soon turns him into a star, but starts to treat him badly and won't let him see Mac. When Bloo tries to quit, he is informed that he signed adoption papers and has no choice in the matter. Can Mac and Bloo ever be re-united?
After beating Mac's high score in a video game, Bloo goes to rub it in his face at school. But he is horrified when he comes to the conclusion that Mac is a nerd. When Mac arrives, Bloo quickly works to make Mac cool, but none of their ideas work. But just as Mac says he doesn't care about being cool, the coolest kid in the school, Jamez Withazee tells him that the fact that he doesn't want to be cool, makes him cool, and invites him to 'The Rock.' As Mac is not at Foster's at 3 o' clock because Jamez tells him that Foster's is for nerds, Mr. Herriman is very quick to ensure that Bloo gets adopted. Now Bloo must find Mac, while at the same time avoiding adoption! Will bloo find Mac before he gets adopted?
During the production of the home's newspaper, a new friend returns to Foster's. Well, not new, but very old indeed. In fact, it just so happens that it's Uncle Pockets, the very first imaginary friend to come to Foster's. Uncle Pockets' charm drives all the other friend's attentions to him, making Bloo jealous. Bloo then decides to try and expose Uncle Pockets as a fraud through the home's newspaper. Then later, when he thinks he hears that Uncle Pockets is trying to kill Mr. Herriman, Frankie, and Madame Foster, he stops at nothing to stop him before it's too late!
A rich benefactor is considering giving money to a charity, and visits Foster's to see if it is worthy. Mr. Herriman gets Mac and Bloo to keep Coco out of the way but in the end it is only when the benefactor mistakes Coco as Mr. Herriman's wife that he considers Foster's, and invites them to his mansion where he will decide which charity gets the money. Mr. Herriman then tries to teach Coco to be sophisticated, while Mac and Frankie teach Bloo sarcasm, since he didn't understand that Mr. Herriman was being sarcastic when he promised them two jet cars. At the mansion it is a competiton to see who will win the money. Can Coco and Mr. Herriman win the money for Foster's? And what about Mac and Bloo who enter as 'Jet Cars for Tiny Tots'?
Eduardo runs away from the home to prove that he's not a coward. Meanwhile, Terrence is looking for an imaginary friend to compete in the Extreme-O-Saur Battle, and he comes across Eduardo. Terrence uses him to fight against huge imaginary friends at the dumpster. Mac, Bloo, Wilt, and Coco must search for Eduardo.
Richie Wildebrat, a kid at Mac's School, keeps braging about his imaginary friend, Blake Superior, and he keeps bragging about him winning the imaginary friend talent show pageant. Mac wants to beat him so it can end Richie's bragging, so he asks Bloo to enter in the pageant, but Bloo doesn't want to, then he gets the hiccups, which Blake says is ridiculous, so Bloo enters. How is Bloo going to beat Blake Superior with his hiccups?
Mac and Bloo ask Mr. Herriman to go camping out in the wilderness. Madame Foster thinks it is a great idea to get away from all the civilization for a while, but when Bloo eats all of the food on a camping trip, everyone struggles to survive. Adversity sets in as Mr. Herriman encounters real bunnies, Madame Foster fights against a bear, Wilt gets stuck in quicksand, Coco has trouble casting a live fish, and Eduardo feels upset about Mac and Bloo trying to hunt the animals down for food. Will they ever make it out in one piece?
Duchess is adopted by Mac's neighbors, and Foster's doesn't want to take her back. Meanwhile, Terrence told Mac that his mom is thinking about moving to Singapore. It's up to Mac and Bloo to get rid of Duchess. They try to frame Duchess for what they did to their home, but it only makes the family love Duchess even more. Mac and Bloo have no choice but to return her back to Foster's. However, Terrence decides to help the others back at Foster's Home to keep Duchess away.
Goofball John McGee comes to Foster's, who is a total pain. Frankie thinks he's a teenage kid passing himself off as a imaginary friend, who always needs help on homework, needs to wash his jerseys, and eats all the food that Frankie bought from the store, but everyone else believes otherwise. So now, Frankie is out to prove him as a fraud. But is he really the fraud Frankie thinks he is?
Mac enters a contest to win a trip to Europe. But when the gang tries to pack at the last second, everyone has delays that keep the gang from going. While at the same time, Mac is getting more upset. Will Mac and his friends be able to make their flight to Europe on time?
After Mac bumps into a girl named Goo when he gets something out of a tree, she thinks that Mac is her boyfriend, and Goo begins visiting Mac everyday at Foster's. With her hyper active imagination, she creates a new friend one after another, which causes a big problem for the other imaginary friends in the house. After she creates so many imaginary friends that it crowds the whole house, the others have to sleep in the Foster's bus. Can Mac stop Goo from creating so many friends?
Mr. Herriman becomes addicted to carrots. Meanwhile, Bloo tries desperately to avoid eating Frankie's "it" by doing bad things, but Mr. Herriman ignores or misinterprets the bad deeds and sends everyone else to bed with no supper instead. Also, Frankie learns to cook "it" under the guiding (and painful) wooden spoon of Madame Foster.
When Eduardo gets fleas while getting one of the house’s imaginary puppies to take a bath, he becomes discontent as the fleas are driving him mad. However, despite the way he feels, he decided to keep the fleas on him because he believe they’re his friends; though Frankie and Mr. Herriman want none of it and they decide to go to drastic lengths to get the fleas removed. Meanwhile, Bloo wants to get some fleas of his own and he does anything possible in order to attempt to get Eduardo to share them.
Mac makes a home movie about Foster's Home for his school project, but Bloo edits it into a blockbuster hit. This leads him to be entered in the state student film festival. With Bloo's help, they make T-Rexatron III Alien Wolfhound, A Prequel In Time: The Unrelenting. Eduardo, though, thinks he has a problem breaking wind when it was Bloo doing sound effects and doesn't want to be in Bloo's movie which forces Bloo to make him to a computer animated character in his movie. What happens at the wrap party and how will the movie turn out?
Everyone in Fosters is sick of Herriman's rules, so Frankie decides that she shoud run for president. Bloo hears about this and decides to take an oppurtumity. Bloo seems to have the most chances of winning but Frankie tells them that she helped them every day. Frankie now is having the upper and but Herriman might have a trick under his rabbit sleeve. Who will win in the end: Franke, Bloo,or Mr. Herriman?
When a recent adoption leaves a room at Foster's vacant, Bloo, Coco, Wilt, and Eduardo all fight over it, along with another friend named Peanut Butter. Everybody soon starts to make contests to see who will win the room, which leads Bloo to try to make contests that he can cheat at. how will they settle this fight and who will win the room?
When Mac taks his classmates on a field trip to Foster's, everybody loves Coco and Bloo wants all the attention after Coco lays eggs with imaginary friend trading cards. Soon, when Bloo throws eggs at everyone, they run away and now Coco hates Bloo. When all the friends start trading and collecting the cards, soon Bloo gets intrested and starts to collect them all. Will Bloo collect all of them without Coco's help?
When a hoard of imaginary Santas enter the house, Mac starts to believe that there is no such thing as Santa Claus. Bloo decided to try to prove him wrong, in hopes of getting the real Santa to deliver him more presents, so they go about trying several experiments that would logically prove Santa is real. Will Mac be able to regain his faith in Santa Claus or will this be the worst Christmas ever for Foster’s and Mac alike?
