Jimmy Valmer solely creates the funniest joke in the world, yet Eric Cartman takes half the credit for it. Meanwhile, rapper Kanye West fails to understand the joke, and resents it being directed at him.
Cartman arrives at Jimmy Valmer's house, saying that he "wants" to hang out with him because Stan and Kyle are mad at him for some reason. Cartman then asks Jimmy for some food. Jimmy tells Cartman there are fish sticks in the freezer, and Jimmy comes up with a joke, that goes: "Do you like fishsticks?" "Yeah." "You like to put fishsticks in your mouth?" "Yeah." "What are you, a gay fish?"
The joke becomes very popular, first gaining fame in South Park, then even airing on television programs. However, the joke's creator is unknown. Cartman then takes credit for making the joke, even though it was all Jimmy's idea. Craig's idea is just to give Cartman half saying that it is the best you could hope for from Cartman, while Kyle's is to stand up for himself. Even when Jimmy tells Cartman this, Cartman actually has false flashbacks, each time giving himself more and more credit for the joke and saving Jimmy from a black widow, slaying a dragon, burning Jew-Bots (by somehow having the power to turn into flames), and people telling him he's not fat.
Kyle tells Cartman that he actually believes that Cartman believes he made the joke, that people like him have egos that will do whatever they can to protect themselves and that his ego is so messed up that he goes through mental gymnastics to actually convince himself he is awesome when he is really just a douchebag. Meanwhile, the only person who does not get the joke is Kanye West, who thinks people are starting rumors about him being a "gay fish." (He points out that he is neither homosexual or a fish, and even goes to the extreme of getting a doctor to show that unlike fish he has no gills.) and no matter how slowly and clearly they explain it, he still does not get it.
Carlos Mencia then takes credit for the joke, and Kanye goes to his house to beat him up and ask why he was starting rumors about him. Carlos then gets killed by Kanye, who nearly decapitates him with a baseball bat. Cartman and Jimmy then go on the Ellen DeGeneres show, where Cartman takes most of the credit for the joke, since Jimmy was interrupted by Cartman because he stutters. Jimmy then asks how Cartman can live with himself, where then Kanye and his group tie them up. While Cartman then says that Jimmy is actually the 'twisted one', and that Cartman believes that Jimmy actually believes that he created the joke and that his ego is so bloated that he goes to incredible lengths to make himself part of things. Kanye then "realizes" that people were trying to help him, so he goes out to the dock and jumps in, going to live as a gay fish. A song called "I'm a Gay Fish" then starts playing. Kanye somehow is able to breathe underwater, and the episode ends with him humping a grouper.