Barnacle Boy is the sidekick of Mermaid Man. He is voiced by Emmy Award-winning comedian as well as actor Tim Conway. He, along with Mermaid Man, are superheroes. He is a parody of both Aqualad and Robin. Barnacle Boy was said to be 68 years old in Mermaid Man and Barnacle Boy V.
In "Mermaidman Begins", it seems that Barnacle Boy was a normal human who used to be a sailor boy that would scrape barnacles off the sides of ships. That sailor job also gained his name of "Barnacle Boy."
Barnacle Boy is thin, bald, has a large nose (similar to and bigger than Squidward's), has puffy ears, a black mask and a turquoise neckerchief. He also wears dark blue rubber gloves, boots, a red T-shirt, and rubber black shorts. Being younger, he is more sane and self-aware than Mermaid Man. However, Barnacle Boy is also more cranky and rude. He often calls Mermaid Man an "old coot". He is revealed to be 68 years old in Mermaidman and Barnacleboy V. As younger self, instead of a black mask, he wears glasses and is much taller. Also, as younger self, his neckerchief is space-control.
Barnacle Boy possesses powers similar to Mermaid Man, though he lacks the belt powers. Barnacle Boy also has "Sulfur Vision" (a form of Heat Vision), which Mermaid Man has never been shown to have. Like Mermaid Man, his powers do not work as well as they used to.
Despite being a senior citizen, Barnacle Boy is still treated like a child by his mentor, much to his disdain. In "Mermaid Man and Barnacle Boy V", when Mermaid Man orders a Pipsqueak Patty (a very small version of a Krabby Patty, intended for children) for Barnacle Boy at the Krusty Krab, they get into an argument which ultimately results in Barnacle Boy becoming a villain and forming a group called "E.V.I.L." (Every Villain Is Lemons) with Man Ray and the Dirty Bubble. After a protracted fight with Mermaid Man and the "International Justice League of Super Acquaintances (whose costumes and powers are assumed by the main characters of the show), which E.V.I.L. actually wins, he and Mermaid Man patch things up. Barnacle Man, as he likes to be called, gets a little more respect now (even though he mentions that an adult-sized Krabby Patty actually is too big for him).
In the video game Battle for Bikini Bottom, it is revealed that Barnacle Boy has a son, a daughter-in-law, and four "screaming" grandchildren.
Barnacle Boy is tired of everybody calling him a boy.
He has hair growing out the wrinkles on his liver spots.
Barnacle Boy is taller and narrower than Mermaid Man, and shaped like a sausage.
Barnacle Boy started being a Superhero in 1960s like era.
Barnacle Boy has a case of cauliflower ear, in which the ear becomes swollen and deformed. This condition is commonly seen in elderly people.
His voice actor, Tim Conway, portrayed the character of Dorf.
Interestingly, there was a Dorf episode where he plays bingo, and in Mermaid Man and Barnacle Boy VI: The Motion Picture, the two heroes are playing bingo (though Mermaid Man gets it wrong by shouting "Bungo!" instead of "Bingo!", much to Barnacle Boy's annoyance).
Just like Mermaid Man, Barnacle Boy's real name is Tim, which is actually the name of his voice actor, Tim Conway.