Mermaid Man is portrayed as a stereotypically overweight senile elder, and appears to suffer from slight memory loss as he is easily confused by others' behavior, though this also could be partly credited to his hearing loss. As a young adult, Mermaid Man had a muscular, athletic build, but the elderly Mermaid Man is obese and out of shape. As opposed to his sidekick, Barnacle Boy, he is slightly less grouchy and somewhat more tolerant of SpongeBob's ecstatic optimism, but only to a certain extent as SpongeBob's slips or mistakes have triggered serious consequences before in the past, and his partner seems annoyed with Mermaid Man's absentminded tendencies. Despite this, Mermaid Man has maintained some of his abilities as a skilled crime-fighter, though some of them have comically been shifted in a fashion more appropriate with stereotypes commonly associated with his age; however, few of his admirers seem particularly bothered by this.
|~ Mermaid Man|
- They are a parody of the following superheroes:
- In Mermaid Man's early appearances, he was voiced by the late Ernest Borgnine. After Borgnine's death, Joe Whyte is now the current voice actor for Mermaid Man.
- Young Mermaid Man was voiced by the late Adam West (who also portrays Batman in the 1966 live-action television series of the same name).
- Mermaid Man is about 5'9 and 225 lbs while Barnacle Boy is about 5'6 and 160 lbs.
- In Mermaid Man's early appearances, his belt is yellow (similar to the Silver Age Aquaman's belt), but in his later appearances beginning with "Mermaid Man and Barnacle Boy IV", his belt is purple with a metallic-blue M.