Radioactive Man is a famous fictional character of whom Bart is a fan in the famous animated series The Simpsons. He is a superhero who acquired his powers after surviving an atomic bomb explosion. His catchphrase is "Up and atom" and he is part of the Superior Squad, a group of superheroes inspired by the Justice League or the Avengers. Bart being an absolute fan of this character and his adventures, he participated in the casting for Fallout Boy, Radioactive Man's companion when a film adapting the adventures of Radioactive Man was filmed in Springfield. Unfortunately he didn't get the part because he was just a few centimeters too short.