"Homer the Whopper" is the season premiere of season 21 and aired on September 27, 2009. The episode was written by Seth Rogen and Evan Goldberg (who claim to be "obsessed" fans of the show) and was directed by Lance Kramer.
Comic Book Guy's comic book hero, Everyman, becomes a big hit in Springfield, and he agrees to a movie version. CBG insists that he chooses who plays the lead role, and gives the part to Homer. However, the movie company hire a personal trainer for Homer, called Lyle, so that he can get fit for the part. When Lyle leaves, Homer puts on weight again, and the movie is a disaster. The company offer CBG the chance to direct a sequel if he pretends he liked the movie, but he criticises it.
Comic Book Guy creates a new superhero called Everyman who takes powers from other superheroes by touching their comic books. Homer is cast as the lead in the film adaptation. To get Homer into shape, the movie studio hires a celebrity fitness trainer, Lyle McCarthy to help him, but Homer has trouble sticking to his new healthy regimen.
Bart and Milhouse convinced Comic Book Guy into publishing a comic book he wrote titled Everyman, in which the title character, an overweight average man called Avery Mann can absorb superpowers from the characters of comic books he touches. The comic becomes an instant hit, and many Hollywood studios become interested in making it into a movie. Comic Book Guy agrees to let Everyman become a movie, but only if he can pick the star. When Comic Book Guy sees Homer, he considers Homer would be perfect for the role, as he wants Everyman to be played by a middle-aged fat man like his character. But the studio executives realizes that audiences want a physically fit actor for the role, so that people will see the everyman they 'want' to be rather than the everyman they are. They hire celebrity fitness trainer Lyle McCarthy to make Homer fit. After a month, Homer becomes fit and muscular, so the movie begins production.
Soon afterwards, however, McCarthy leaves Homer for another client. Without McCarthy to keep him fit, Homer starts eating again and gains all the weight back. Homer can no longer fit into his costume or even his trailer, and the movie begins to go over budget. The studio executives and Comic Book Guy worry that the film will not be successful. The final version of the movie features scenes with the fat Homer and the physically fit Homer merged, upsetting the audience. After the premier of the film, McCarthy returns and offers to make Homer physically fit again, which Homer accepts. The studio executives offer to let Comic Book Guy direct the sequel, on the condition that Comic Book Guy lie to the fans and say he liked the film. Comic Book Guy rejects the offer and openly criticizes the movie online.
Seth Rogen and Evan Goldberg, writers of the film Superbad, asked the producers of The Simpsons if they could write an episode. They were invited to the writers room where they pitched several episode ideas. One was accepted, and they wrote an outline with the help of some feedback from the regular writers. The table read took place in August 2008, and production on the episode began soon after that. Rogen later said "we sat down for a read-through and three hours later I'm in a studio improv-ing with Homer Simpson, it was the single greatest day of my life."