Mermaid Man and Barnacle Boy are a duo of fictional characters from the American animated television series SpongeBob SquarePants. They were respectively voiced by guest stars Ernest Borgnine and Tim Conway. Mermaid Man and Barnacle Boy first appeared in the eponymous season one episode that premiered on August 21, 1999, and were since featured as recurring characters. Following the deaths of Borgnine and Conway in 2012 and 2019 respectively, the characters have been relegated to non-speaking cameos