He is a much bigger and more infantile version of SpongeBob. His arms and legs are very chubby and he has one buck tooth.
Role in episode
When the Flying Dutchman enters SpongeBob's brain to see how scary it could possibly be, he is astonished by all of the things in one brain. He says he still is not scared and SpongeBob points out that naked baby pictures always scare him. Then, the giant baby SpongeBob comes and the Flying Dutchman is terrified enough to get out of his ship, far away from SpongeBob.