Cthulhu is PBed by comedian Chris Titus.  He is played by Jerry.

Cthulhu is drawn mostly from the original Call of Cthulhu story.  He is a Great Old One, arguably one of the more powerful beings in the multiverse.  It is implied that he's more powerful than the "Earth deities", but it's also pretty heavily implied that these deities don't even exist in the Mythos reality, so there was no real way to prove that.  He is capable of all sorts of things.  He is physically extremely powerful, capable of throwing down with the best of them.  He is an extremely powerful telepath, capable of literally tearing minds apart with no real effort.  He is technically capable of possessing people, but now that he's free from R'lyeh he really isn't going to do that unless necessary.  He is capable of temporal distortion, though he cannot actually shift through time, that's more Yog-Sothoth's bag.  He is capable of flight, and will quite enjoy it, given his long, LONG imprisonment.  He's also capable of large-scale teleportation, though he will usually fly somewhere, if he has the time.  He is a vastly powerful mage, though his magic is very unique.  He is, however, locked into his human form, and thus cannot go on a giant monster rampage.

He is not going to "act up", mostly because he senses the presence of the Endless, which are, in his opinion, the only beings in the universe that are capable of destroying him.

His personality is best described, at this point in time, as a scientist.  Cthulhu is sometimes identified as a High Priest of the Great Old Ones, and due to the extremely formuliac nature of the Mythos magic, being a High Priest would likely be somewhat equivalent of being a scientist.  He is at present fairly emotionless, due to not understanding emotions, but he is not averse to understanding the monkeys better.

So that he may one day more efficiently devour all that lives, of course.