 Mermaid Man and Barnacle Boy first appeared in the eponymous season one episode that premiered on August21, 1999, and have since been featured as recurring characters.Following Borgnine's death in 2012, Mermaid Man and Barnacle Boy were reduced to non-speaking roles.Mermaid Man and Barnacle Boy are two elderly superheroes who live in a retirement home and are stars of SpongeBob and Patrick's favorite television show.