Cthulhu is the secondary antagonist of Coon vs. Coon and Friends, and serves as the muscle for The Coon, aka, Eric Cartman.
Coon vs. Coon and Friends
Cthulhu is accidentally released from his sunken city when the drillers of the BP Oil Company were drilling in the moon as an attempt to cancel out their other spills. Eric Cartman comes to him as the Coon, and he manipulates the Great Old One into helping him massacre people throughout the world that he viewed as evil and malicious whether it be synagouges, hippes, or even Justin Bieber himself. Earlier, Cartman manipulated the heroes of the Coon Club into going outside with him, and he then has the Great Old One banish his former friends into a dark void.
Mysterion/Kenny discovers that his parents were Cthulhu worshipers, and that he was immortal. This explained how he always came back in the next episode after his death, and for why no one ever questioned Kenny's absence from the episode the next day. He then learns that only he could kill Cthulhu, since only an immortal being could kill another immortal being.
At the climax of the episode, Mint Berry Crunch is met by his father who explains to him that he was sent to Earth as a means of stopping evil from dominating the world. With his powers, he manages to subdue Cthulhu, save the other heroes from the void, send Cthulhu back into his dimension imprisoning him, and he also manages to seal the hole that was drilled in the Gulf of Mexico by the BP Company. Cartman is later imprisoned in the Coons' secret base.