SpongeBob SquarePants Season 3 Episode 9

Krab Borg: SpongeBob stays up late one night watching a sci-fi film where robots take over the world. He comes to work paranoid and Squidward scoffs at him. Through a series of wild coincidences, SpongeBob gets it in his head that Mr. Krabs is a robot and convinces Squidward the same thing, too.