Sheldon J. Plankton

Sheldon J. Plankton, more commonly known as Plankton, is the antagonist of Pineapple Playhouse and of the SpongeBob SquarePants franchise. He is a planktonic copepod who runs the Chum Bucket restaurant alongside Karen, a waterproof computer who is his sidekick and wife. The Chum Bucket is highly unpopular in Bikini Bottom because it serves chum, a type of bait made from fish meat.

Overall, he is the main antagonist of the franchise. Plankton despises his rival, Mr. Krabs, for running a successful restaurant because his own business rarely gets any customers. He is incredibly jealous of Mr. Krabs and his success. His main goal is to steal Krabs' secret formula for Krabby Patties and running Mr. Krabs out of business. Karen gives him a variety of plans to steal it, but their efforts always end up failing in the process.

Plankton is voiced by Mr. Lawrence, one of the show's staff writers.