Original: Sheldon J. Plankton, the owner of the Krusty Krab's rival restaurant, The Chum Bucket, is always trying to find out the mystery ingredients for the Krabby patty formula.
Simplified: Sheldon J. Plankton (usually called Plankton) - the evil genious owner of the Chum Bucket restaurant, who hates the Krusty Krab and wishes to take the Krabby Patty formula.