Cyd and Shelby travel back to relive one of their favorite memories from middle school, but the moment winds up being totally different than what they both remembered. Now, they begin to question everything that happened on that particular day.
When Shelby’s new lab partner, The Rob, can’t stop being mean and annoying, the girls travel back in time to try and find out why he’s such a jerk.
Cyd and Shelby go back to change the past so that Barry can meet his childhood science hero. However, when they return, they realize Barry and Naldo have changed as well and are now terrible rock musicians instead of aspiring scientists.
When the girls are assigned to do a report on the 1970s disco era, they decide to travel back and experience the 70s firsthand and land in the midst of turf battle between the disco and punk kids.
Cyd and Shelby discover a major clue to the future lab memory and it is somehow tied to Barry's Science mentor Janet Smythe, who also employs Shelby's dad.
Cyd and Shelby take a bite out of the Big Apple when they use Barry's new invention to telepathy themselves to the NYC Central Park Spooktacular only to end up trapped in a haunted house.
When Cyd and Shelby go back to kindergarten to celebrate their friendship anniversary and relive the day they first met, they begin to change back to their five-year-old selves.
When the girls discover inventor and GDD CEO Janet Smythe is behind the future lab, they decide to fight back and travel to the past to stop Janet from starting the corporation. Their plan seems to work until they realize they also stopped other major events from happening in their lives, including them living together and Barry and Marci falling for each other.
Things spin out of control when Cyd travels back to Christmas the year before to try and figure out the perfect gift for Shelby. Meanwhile, Barry and Naldo's Winter Wonderland experiment sparks an elf war with Bret and Chet leading the charge.
Cyd and Shelby use time travel to attend two different events on the same night; the plan backfires when they meet boys at both events.
When Shelby's adventurous Grandma Rita comes to visit, the girls learn time travelers were responsible for setting up Shelby's grandparents and they jump to the 1950s to investigate.
Diesel swallows a time travel tracker and disappears; Shelby and Cyd hurry to track him down before he's lost forever.
When the girls discover their future-selves have asked to lose their time travel abilities, they leap to the future and see that evil Janet Smythe is somehow involved. Meanwhile, Barry learns Marci is planning to break up with him.
When Janet unexpectedly invites herself over to Shelby's for dinner, the girls use the opportunity to find out what she knows about time travel.
While Janet tries to uncover the secret behind time travel, the girls decide they need to take her down once and for all!
A princess named Daisy has come through the time rift from the 16th century and finds herself at Cyd and Shelby's school.
Bret and Chet worry about their sixth grade dance; haunted by the nemories of their own experience, Cyd and Shelby go back in time for a do-over.
The girls decide to take Daisy on an official "Epic Girl's Day" at the mall since she might be here longer than expected.
Barry is too busy to help Shelby build her website so she takes matters in to her own hands; Cyd and Naldo win a boat and try to hide it in the backyard.
Cyd and Shelby watch roller derby against Astrid's wishes; they find out Shelby's mon has been lying.
When Cyd tries to protect Diesel from Barry’s wolf serum experiment, she accidentally gets the serum on herself and turns into a menacing werewolf. Now Shelby must try and figure out how to get her best friend back before the she-wolf destroys their high school’s Halloween carnival.
Shelby and Cyd get their first jobs at a fudge kiosk at the mall, but the job is not all that Shelby thought it would be.
When Daisy reveals that she's engaged to Sebastian, a young man she's never met, Cyd and Shelby decide to travel to the 16th century to help her break off the engagement.
Shelby and Cyd encourage a homesick Daisy to incorporate a festive 16th-century tradition into their annual Christmas party.
Shelby gets trapped in the 16th century after trying to save Daisy from marriage, so the friends join forces to help rescue her.