Barnacle Boy is an elderly superhero, and Mermaid Man's sidekick. He is known to be a lot more stable than Mermaid Man and does not shout "EEEVIIIIIILLLL" like he does. Barnacle Boy is very similar to Squidward in that he has a near identical nose, and he is always grumpy about something. However, he is more tolerant of SpongeBob than Squidward is, although they both find him annoying. Barnacle Boy does not appear in any Rise of Sqeegee episodes until The Rise of Sqeegee 8, which is also the first episode Mermaid Man appears in.
Barnacle Boy's most powerful attack is turning into a cheetah and rushing his enemy. It is unknown how he acquired this technique, but he was seen using it on Black Luster Sqeegee in ROS8. In the same episode, he was defeated by Black Luster Sqeegee and hasn't appeared since.