Mermaid Man and Barnacle Boy are a duo of fictional characters from the American animated television series, SpongeBob SquarePants.

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.

[1][2] 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.

[7] Despite this, Mermaid Man has maintained some of his abilities as a skilled crime-fighter, though some of them have been comically shifted to reflect stereotypes commonly associated with his age; however, few of his admirers seem particularly bothered by this.

The episode "Mermaid Man Begins" reveals that, through a series of meticulous and intricate events, he and his friend were suddenly equipped with aquatically themed superpowers when they left the microwave on long, causing their popcorn to become slightly overcooked.

[6] While he was as muscular as Mermaid Man was in their younger days, he has a slender physique and large nose that slightly resemble those of Squidward Tentacles as an elder.

Series creator Hillenburg described the guest appearances of Ernest Borgnine and Tim Conway as "so fantastic."

Joe Alaskey voiced Mermaid Man for the video games SpongeBob SquarePants: Lights, Camera, Pants!

[19] As with Mermaid Man, Barnacle Boy's appearances were reduced to non-speaking roles or portrayal by other characters (generally Patrick Star) since Borgnine's death.

On September 27, 2018, SpongeBob showrunner Vincent Waller confirmed that Conway would not reprise his role as Barnacle Boy again.

[21] In The Patrick Star Show episode "Super Sitters", a younger Barnacle Boy is voiced by Tom Kenny.