Complex sentence: Sheldon James Plankton, or simply Plankton, is a character in the Nickelodeon animated television series "SpongeBob SquarePants", even though in some episodes he is shown as a protagonist or an antihero.
Split into simpler sentences: Sheldon James Plankton, or simply Plankton, is a character in the Nickelodeon animated television series "SpongeBob SquarePants". Although usually an antagonist, he is frequently shown as a protagonist or an antihero.