Cthulhu is a Great Old One (Gods of interdimensional origins), originally created by H.P. Lovecraft. He makes his first appearance in "Coon 2: Hindsight" and subsuquently appears in "Mysterion Rises" and "Coon vs. Coon & Friends".
In "Coon 2: Hindsight", when DP (formerly BP) drill a hole in the Gulf and accidentally reaches another dimension, they attempt to rectify the problem by drilling on the moon to change its gravitational pull on the Earth, hoping that this will solve the problem. However, all this does is make the problem a whole lot worse when it releases Cthulhu, a very large green tentacle headed monster with glowing orange eyes, massive wings and long spindly arms, from his interdimensional slumber. A news reporter explains Cthulhu is expected to reign over the Earth in a dark period of around over 3000 years, during which he would drive the world to madness and enslave humanity as members of his cults.
As he continues his rampaging in "Mysterion Rises", Cartman (dressed as the Coon) approaches the monster in New Orleans where he attempts to sway Cthulhu to be his ally and help him destroy his friends and former teammates Coon & Friends. Although Cthulhu takes enough time to listen (or at least observe) Cartman's rantings, he grows bored and attempts to leave, at which point Cartman manipulates Cthulhu by behaving overly cute. As a result, Cthulhu grows oddly fond of him, and proceeds to do Cartman's bidding. Cartman and Cthulhu proceed to rampage across the world, attacking all the things that Cartman alone deams evil (The Jewish People, San Francisco, and Hippies).
Their next act of course involves Cartman ordering Cthulhu to send Coon and Friends to a dark oblivion. With his friends gone, in "Coon vs. Coon and Friends" Cartman and Cthulhu continued cutting a path of destruction, massacring Justin Bieber and his fans, until they are defeated by Mint-Berry Crunch, who had discovered his alien powers, and Cthulhu is sent back to its world, along with his demon armies, and the holes in the Gulf of Mexico are filled.
Cthulu is a massive, interdimensional demon. He is massive, towering over a DP (formerly BP) drilling platform. He has two massive and long arms, with sharp talcons. He has two large bat-like wings on his back. He also has two clawed back legs. He has a long tail, similar to that of a prehistoric pterosaur. Its use seems to be to help his direct himself through the air. His head has to massive, yellow eyes, similar to that of a dinosaur's. Instead of a mouth, he has a large set of tentacles, that move whenever he "talks", or makes vocal sounds.
As shown when he attacks the Gulf of Mexico, Cthulhu is truly a god, and is possibly the most powerful being in existence, (although he is still defeated by Mint-Berry Crunch). His powers include, but are not limited to:
- Godlike Strength: Cthulhu has enough strength to easily rip a massive Ferris wheel off of its hinges, as though it were made of paper, and hurls down upon unlucky humans.
- Lightning Touch: Cthulhu can release lightning from his hands, which can completely incinerate a person in seconds.
- Dimensional Travel: Cthulhu has shown to be able to make an enemy be sent to R'lyeh, his supernatural capital of his empire, by a wave of his hand.
- Flight: Due to his massive wings, Cthulu can fly across large distances, such as the distance for the Moon to the Gulf of Mexico, in seconds.
- Demon Command: As shown by the wave of creatures that attacked the Gulf of Mexico, these were probably his servants, meaning Cthulhu has control over possibly trillions of demons, probably gained by his command of dimensions and his ferocity. The "demons" pouring across dimensions heavily resemble the "Elder Things" (also created by H.P. Lovecraft) from the Cthulhu Mythos universe, who actually work independently of Cthulhu, which may mean he is not in control after all. However, in the Cthulhu Mythos, he has command of a race called "The Star Spawn of Cthulhu" who, oddly enough, don't appear in South Park. Of course, considering how South Park often modifies whatever it parodies for humor, it's possible that those creatures are actually his servants in South Park.
- Immortality: In the original story "Call of Cthulhu" by H.P. Lovecraft, and "Trail of Cthulhu" by August Dereleth, Cthulhu would regenerate from any wound, up to and including a nuclear bomb. This is supported in the show when Kenny (as Mysterion) mentions Cthulhu being an immortal, and that only an immortal can kill another immortal. He also demonstrates the ability to survive in the vacuum of space.
- Cthulhu was first described in twentieth century author H.P. Lovecraft's work "The Call of Cthulhu" which was first published in the Wierd Science magazine in the late 1920's and is arguably one of Lovecraft's most well known stories and has spawned many sequels including many written by seperate authors.
- It is possible that the reason that Cartman and Cthulhu get along so well is because both Cartman and Lovecraft (the creator of cthulhu) are anti-semites.