The first season of the American animated television series SpongeBob SquarePants, created by former marine biologist and animator Stephen Hillenburg, aired on Nickelodeon from May 1, 1999, to March 3, 2001, and consists of 20 half-hour episodes. The series chronicles the exploits and adventures of the title character and his various friends in the fictional underwater city of Bikini Bottom. The show features the voices of Tom Kenny, Bill Fagerbakke, Rodger Bumpass, Clancy Brown, Mr. Lawrence, Jill Talley, Carolyn Lawrence, Mary Jo Catlett, and Lori Alan. Among the first guest stars to appear on the show were Ernest Borgnine and Tim Conway voicing the superhero characters of Mermaid Man and Barnacle Boy, respectively.

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, who both previously starred in the 1960s sitcom McHale's Navy. Mermaid Man and Barnacle Boy first appeared in the eponymous season one episode that premiered on August 21, 1999, and have since been featured as recurring characters. Following the actors' deaths, the characters have been relegated to non-speaking cameos after creator Stephen Hillenburg requested not to recast the characters.