The Creepy Cool Mutant Alien is a fictional alien that appears in the Grotesquely Grim Bunny comic in the episode "Tales of Grotesquely Grim Bunny". When Arthur first saw it, he imagined it leaping out of the page and hissing at him. In Arthur's later nightmare, Buster was casually having an ice cream sundae with the alien. The alien hissed at Arthur once again, but Buster told it to watch its temper.