Plankton

Sheldon J. Plankton is an antagonist of ''Spongebob Squarepants. '' He is a plankton who owns the Chum Bucket, the rival restaurant to the Krusty Krab. As the self-proclaimed archenemy to Mr. Krabs, he constantly tries to steal Krabs' secret recipe for Krabby Patties, but is always unsuccessful (except, temporarily, in The SpongeBob SquarePants Movie). Sometimes, not only does he wish to run Mr. Krabs out of business, but he also wishes to rule the world. His wife is Karen, a computer of his creation. Though he is considered the main antagonist of the series, he has been portrayed as a protagonist or anti-hero on several occasions.