Once a Hero (1987)

The creator of comic superhero Captain Justice, Abner Bevis, is in a rut, repeating old storylines. The comic's owners want to kill the strip off due to falling sales, and children are losing interest in it. This transfers itself to the world of the comic strip, Pleasantville, where Justice realises his adventures are repeats, and the characters of the world are starting to fade. So Justice crosses into the real world. He finds he has lost his superpowers, but the comic's Gumshoe has followed him and is looking out for him. His antics create renewed interest in the strip. Bevis is inspired to make Justice more contemporary, and the owners agree not to cancel it.