Being a failure in his planet, Comet Guy traveled to Earth for training. On Earth he met Darkwing Duck where he trained him to be a real super hero. He was tricked by Steelbeak into helping F.O.W.L. by getting rid of Darkwing Duck, whom Steelbeak claimed was really a villain. Eventually, however, Darkwing convinced Comet Guy that Steelbeak was tricking him, and, with Darkwing's help, Comet Guy turned his weaknesses into strengths, defeated F.O.W.L. singlehandedly, and returned to Mertz as a worthy hero.
Later, Comet Guy returned to Earth to seek Darkwing's help. He and the other heroes on Mertz had misplaced Mertz's only non-superpowered citizens, Ordinary Guy, whom the various superheroes took turns rescuing. Comet Guy told Official Guy that Darkwing, as a hero without powers, to be the new Ordinary Guy. During his time on Mertz, Darkwing, as the new Ordinary Guy, attempted to liven things up by convincing Comet Guy to pretend to be a villain and be the one to endanger him. But Comet Guy's heart wasn't in it, and he saved Darkwing from his own death trap.
Eventually it was revealed that Ordinary Guy had actually grown angry with constantly being bothered by his superpowered neighbors, and had turned evil and invented a machine which stole all of the heroes' powers and bestowed them upon himself, transforming him into Extraordinary Guy. Darkwing however defeated him and reversed the effect of the machine, returning Comet Guy's powers.
Comet Guy has the ability to shoot fireballs, fly, super strength and super speed. However, he is dull witted and has a weakness: the sound of a bell makes him dance, and he cannot stop dancing until he hears a whistle. A failure on his planet, Darkwing trains him to turn his weaknesses into strengths. Darkwing later learns he comes from a planet where everyone is a superhero.
- Comet Guy was supposed to appear in season 4, but the show was canceled.