Sheldon J. Plankton

Sheldon J. Plankton A.K.A Plankton is one of the two main antagonists from the show SpongeBob SquarePants, alongside his computer wife Karen. He is a planktonic copepod with one eye. He and Karen run the Chum Bucket restaurant, but it gets no business. Plankton has a rivalry towards Mr. Krabs, whose restaurant The Krusty Krab is very successful. Plankton and Karen come up with various schemes to steal Krabs' recipe for Krabby Patties, but the plans always fail (usually due to Plankton's own mistakes).

History
Plankton and Mr. Krabs were great friends when they were young. They created the Krabby Patty together after the most popular burger joint got shut-down. After everyone had a patty it made their stomachs ache and cramp. After they made enough money they got in a fight and each got half of the recipe. Mr. Krabs got the half that had everything on it but the ingredient that made everyones stomachs ache. That ingredient was chum. So ever since then Plankton has been trying to steal the recipe.