While browsing at a local comic shop, Bart and Milhouse learn that Hollywood producers plan a big budget feature film based on the popular "Radioactive Man" comic books. As luck would have it, the film’s producers choose Springfield as the best place to shoot the picture. Auditions are held in an effort to find a local youngster to play the coveted role of Fallout Boy, Radioactive Man’s trusted sidekick. Bart immediately begins rehearsing for the role. He gives a brilliant reading at his audition, but loses the part when producers feel he is too short.

Instead of using Bart, the producers pick Milhouse. But Bart’s friend is uncomfortable with the publicity and demands suddenly foisted upon him. Production on the film proceeds nonetheless, with Rainer Wolfcastle, star of the popular "McBane" films, appearing as Radio-active Man. Meanwhile, city officials and local retailers greet the production crew with outrageously expensive permit fees and overpriced merchandise. The pressure on Milhouse reaches the breaking point, and unable to cope with sudden fame, he runs away.

A manhunt is organized to find Milhouse, and the production company offers a substantial reward for his capture. In the meantime, producers experiment with editing techniques to save the mega-budget movie just in case their star never returns. But as the people of Springfield comb the city for the missing star, Bart checks his friend’s usual haunts, confident he will turn up. Bart’s suspicions prove correct; he finds Milhouse hiding out in the tree house. Milhouse insists that stardom is hollow and meaningless. Mickey Rooney suddenly appears and tries convincing the budding star to change his mind. But Milhouse prevails and, with the budget having skyrocketed, the production company shuts down. Milhouse thanks Bart for sticking with him throughout the ordeal.