The Sludge Monster is a creature made of sludge. In the comic strip, Garfield watches a movie about the Sludge Monster, which made him paranoid for a week. Later, he, Jon and Liz saw The Sludge Monster Meets Vermin Man at a drive-in theater, with Garfield rooting for the Sludge Monster. It was the ninth time Jon and Garfield had watched the film.