Plankton!
S01E07 - Airdate: 1999-07-31
Runtime: 11 min
SpongeBob falls victim to a scheme by the evil Plankton, Mr. Krabs' minuscule arch-rival with the Napoleon complex. Plankton hides out in SpongeBob's head and takes control of his brain. SpongeBob finds he must fight his own body to prevent himself from handing over the secret Krabby Patty recipe to Plankton.
Episode details and rating from TVmaze.