Barnacle Boy is one of the semi-retired superheroes of Bikini Bottom from SpongeBob SquarePants, the other being Mermaid Man. They are the favorites of SpongeBob and Patrick and both live in a retirement home doing things retired people do. While being on superhero duty, fighting off villains including Man Ray and Dirty Bubble (two arch-nemesises).
Barnacle Boy is depicted as being the undercredited and underappreciated younger sidekick of Mermaid Man. Grumpy and slightly ill-tempered, Barnacle Boy is notable for his brooding, moody disposition and exasperation with his partner's absentminded behavior as a result of old age, and even into his golden years, Barnacle Boy is still treated in a juvenile fashion, coddled in an infantile way.