Mermaid Man

Ernie (or Jim) Huckler, commonly known by his superhero name Mermaid Man, is a semi-retired superhero who lives in Bikini Bottom. He and his sidekick Barnacle Boy are the stars of a show-within-a-show called The Adventures of Mermaid Man and Barnacle Boy, but they are also real superheroes within the SpongeBob SquarePants universe.