Things are going great at the Krusty Krab, until suddenly an alarm begins to blare, signaling an attempt by Plankton to steal a Krabby Patty. Plankton, controlling the patty, escapes outside with it by making a hole in the wall with a laser.
SpongeBob heroically chases after it. After a long chase, SpongeBob finally recovers the Krabby Patty, and is congratulated by the townsfolk, while Plankton walks away sadly. SpongeBob, feeling sorry for Plankton, decides to befriend him.
SpongeBob invites Plankton to go jellyfishing with him, and, realizing he can take advantage of SpongeBob, Plankton goes. At Jellyfish Fields, Plankton remains fixated on evil and destruction, and SpongeBob tries to explain fun by singing The F.U.N. song. Eventually, Plankton starts singing the song as well, first, he sings the an evil version but eventually, he sings SpongeBob's version and seems to finally be having fun. He seems to forget about stealing the formula, and begins to develop a genuine sense of friendship.
When Mr. Krabs sees this, he refuses to believe that Plankton has changed and sets up a trap for them when they come to the Krusty Krab together the next day. He attempts to tempt Plankton with a Krabby Patty, but he seems not to take the bait. After SpongeBob and Plankton leave to go to the movies, Mr. Krabs begins to suspect that Plankton really has gone straight and nice, until he realizes that he actually did take the patty.
At the Reef Cinema, Mr. Krabs appears in front of the projector and shouts "reach into his pocket now and take what he's got!" SpongeBob reaches into Plankton's pocket and finds a Krabby Patty (the other people simply steal from their neighbor's pocket and leave the theater). SpongeBob realizes that Plankton used him to get a Krabby Patty, and Plankton attempts to explain that he realizes now that he only ever wanted friendship, before admitting to everything and running off with the patty. However, he runs directly through the movie screen into a solid wall. Plankton is squashed, badly, and Mr. Krabs flicks him off the wall onto Bubble Bass' hand, who mistakes Plankton for a jellybean and chases him around his hand.
When Squidward says, "How does it feel to be the most hated thing in Bikini Bottom, Plankton?," he ends it with, "It hurts, doesn't it? I know!," possibly suggesting that Squidward knows he too is disliked by the people of Bikini Bottom.
The F.U.N. song was sung during the SpongeBob Krabby Patty Celebration at Nickelodeon Suites Resort in Orlando, Florida.
If you listen carefully, the boot squeak sound effect from "Squeaky Boots" can be heard when the policeman puts the "Honorary Rookie" donut on SpongeBob.
This is the first time Plankton was mistaken as candy (in this episode, a jellybean).