Sheldon J. Plankton better known as Plankton is the main antagonist of SpongeBob SquarePants. Although he is the main antagonist of the series, he is sometimes an anti-hero.
He runs an unsuccessful restaurant called the Chum Bucket along with his sidekick/wife Karen Plankton. He seeks to grow his business by stealing the Krabby Patty formula and eventually take over the world. He has a Napoleon complex due to his very short stature. He is the main antagonist of the show's first theatrical film The SpongeBob SquarePants Movie. and the deuteragonist of its second theatrical film The SpongeBob Movie: Sponge Out of Water.
Plankton works with the help of his sidekick/"W.I.F.E." Karen, a sentient computer who gives him most of his evil plans. He is an evil planktonic copepod and the business rival of Mr. Krabs, the owner of the Krusty Krab where SpongeBob SquarePants works.