Sheldon J. Plankton, better known as Sheldon Plankton, simply known as Plankton is the main antagonist of Nickelodeon's SpongeBob SquarePants franchise. He serves as the main antagonist of the TV show SpongeBob SquarePants, it's first theatrical movie The SpongeBob SquarePants Movie and it's broadway musical, the anti-heroic deuteragonist of the show's second theatrical movie The SpongeBob Movie: Sponge Out of Water and a supporting character in the show's third theatrical movie The SpongeBob Movie: Sponge on The Run.
He runs an unsuccessful restaurant called the Chum Bucket along with his robotic wife/sidekick Karen, and constantly plots to both expand his business (usually by stealing the Krabby Patty secret recipe) and eventually take over the world. He's also the best friend-turned-business rival and archenemy of Mr. Krabs and SpongeBob SquarePants the main titular protagonist with the same name.
He is voiced by Doug Lawrence.