The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents.
- H.P. Lovecraft, The Call of Cthulhu.
Cthulhu is the creation of horror writer H.P. Lovecraft. A form of Ultimate Evil, Cthulhu is the most immediately recognisable and memorable of the Great Old Ones, with its "flabby claws" and "awful squid-head with writhing feelers". It made its first appearance in H.P. Lovecraft's short story, The Call of Cthulhu, published in 1928. Its appearance is detailed twice in the book, first in a small bas-relief sculpture sculpted by a design student based on his dreams of Cthulhu; second in an account from a Norwegian sailor who escaped Cthulhu's city of R'lyeh (which is apparently located not far from New Zealand) and managed to wound Cthulhu. The monster has since become a common fixture in pop culture and sci-fi/fantasy writing as a way to emphasise the evilness of something.
Cthulhu was a favoured method of Sue disposal in the early days of the PPC, but The Rules now dictate that, in the interests of keeping Cthulhu lithe and fit and unSueified, he is to no longer be fed Sues. Unless it would be funny.