An Old Story - S3-E6
Continuity mistake: When Tom and Jon have grown older the next morning and are talking to Aunt Dalia, she wears a headband with two straps hanging down over her right shoulder, which keep changing position from in front / behind the shoulder.
Answer: Whoever created the Masked Mutant comics would still be around to create other comics even with the Masked Mutant dead and the Galloping Gazelle retiring, so Skipper could still receive different comics with all new characters. When Skipper goes into the Masked Mutant's lair, he is hit with a beam of light that turns him into a comic book character so after saying that he's the Colossal Elastic Boy, he turns into the hero at the end of the episode.