The Fairly OddParents (2001)

S1E9 Chin Up

Timmy finally encounters his beloved superhero, The Crimson Chin, but learns that he’s merely a creation of fiction, which plunges the hero into a profound sadness. Determined to help, Timmy sets out to change this reality. In the process, he transforms into his own superhero persona, Cleft the Boy Chin Wonder, to help restore The Crimson Chin's spirit and bring him back to life in a way that only Timmy can.