chthulhu

I believe it was Phil Foglio who wrote a cartoon around the concept of a game called "Escape from Cthulhu." The players open a box, and one of them reads the incantation printed on the inside of the box. A hideous monster appears behind them, with tentacles waving around a mouth filled with needle-sharp teeth, and while the other players wig out, the player with the box reads the second step of the instructions: "Now escape."

I have to say that I've been rather struck by how seminal the Cthulhu mythos have proved to be, especially when you consider how poor Lovecraft was at the actual mechanics of writing. Movies like "Event Horizon" rely on the basic conceit of Lovecraft's work, Cthulhu was a fairly major character (under a different name) in Larry Niven's "World of Ptavvs," and the Old Ones even get mentioned in an episode of Star Trek.