Sheldon J. Plankton

Sheldon J. Plankton, often known as simply Plankton, is an intellectual, green and the main antagonist of the SpongeBob SquarePants franchise. He manages the Chum Bucket, an unsuccessful restaurant located directly across the street from the Krusty Krab. Plankton is married to a computer, Karen Plankton. He is very short at only two inches and can fit on the palm of a character's hand.

Plankton is the main enemy of Mr. Krabs, the manager of the Krusty Krab. He is also SpongeBob's main enemy, although to a lesser degree than Mr. Krabs. Plankton is jealous of the Krusty Krab's success, which is largely contributed to by its signature menu item, the Krabby Patty. Throughout the series, Plankton has tried numerous times to steal the Krabby Patty secret formula, sometimes with help from Karen, so that he can serve Krabby Patties over chum as a menu item. Plankton's schemes always end up in failure, usually from being thwarted by either Mr. Krabs or SpongeBob. Plankton is voiced by one of the show's writers, Mr. Lawrence.