He is a black killer whale with a white dot on his face. He also wears a red cap.
Role in episode
SpongeBob, paranoid while in charge of Goo Lagoon, sees "dangerous" things happening in the water, one of them featuring Billy. Two kids are playing with a ball inside of his mouth, but SpongeBob thinks that Billy is going to eat them. This causes SpongeBob to order everyone out of the water.