F.U.N.

F.U.N. is a SpongeBob SquarePants episode from season one. In this episode, SpongeBob befriends Plankton because he thinks he is lonely.

Plot
Things are going well at the Krusty Krab, until suddenly an alarm blares, 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 jellyfish with him, and, realizing he can take advantage of SpongeBob, Plankton goes. Once there, 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, 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 believe that Plankton really has gone straight, until he realizes that he actually did take the patty. At the cinema together, 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 concrete wall.

Plankton is squashed, and Mr. Krabs flicks him off the wall onto Bubble Bass' hand, who mistakes Plankton for a jellybean and chases him around his hand. SpongeBob then knows never to trust Plankton again and sounds the code red light then Mr. Krabs gets rid of him.