At the start of the movie, Stitch is having a nightmare about turning bad again and causing destruction to Earth. After Stitch wakes up, Lilo tests his goodness level by having him do a few good deeds. Discovering that they are late for hula class, they use their hovercraft to get there.
While at the hula class, Kumu announces that Lilo and her classmates have to prepare to perform at the local May Day festival. Each student is required to create an original dance. After the hula class ends, Mertle insults Lilo, causing them to have a fight, but after taking pictures of the brawl, Stitch forgets to flush the evidence. Kumu thinks that Lilo is not ready for the competition because of the fight with Mertle, but Lilo says that she is ready and "triple promises" to be good.
While preparing for the competition, Lilo and Stitch have a hard time coming up with ideas and Nani wants them to enjoy their family fun night. While watching Them! (film clip courtesy of Warner Bros.) on family fun night, Stitch's past comes back to haunt him and he goes berserk in the house. It seems that after Stitch was created, Jumba did not get a chance to fully charge Stitch's molecules before they were both arrested by the intergalactic police. At first, this glitch causes Stitch to revert back to his old destructive programming, but it will ultimately destroy him if Jumba cannot create a fusion chamber before Stitch's energy runs out for good.