- Tom Kenny (SpongeBob SquarePants / Gary the Snail (voice))
- Bill Fagerbakke (Patrick Star (voice))
- Rodger Bumpass (Squidward (voice))
- Clancy Brown (Mr. Krabs (voice))
- Carolyn Lawrence (Sandy Cheeks (voice))
- Mary Jo Catlett (Mrs. Puff (voice))
- Mr. Lawrence (Plankton / Larry the Lobster (voice))
- Jill Talley (Karen Plankton (voice))
- Lori Alan (Pearl Krabs (voice))
SpongeBob SquarePants — S8E15
Episode: Mermaid Man Begins
Air Date: 2011-09-23
Runtime: 11 min
Overview
SpongeBob and Patrick learn the secret origins of Mermaid Man and Barnacle Boy from the heroes themselves.