Sluzzle Dude is a single-appearance character in The Amazing World of Gumball. He is talked about in "The Lie" when Gumball and Anais make him up as the symbolic figure for the holiday Sluzzle Tag to make everyone happy in January. Since he does not actually exist, he does not make a physical appearance in the show.
According to Gumball, Sluzzle Dude transports himself around the world in a magic van which is led by his Dobermans: Trasher, Smasher, Rancid, Rages Slayer, and Rabies, in order to deliver presents. He delivers his presents, although random and bizarre, through residents' toilets, while the room is traditionally decorated in Sluzzle Tag style and milk and cookies are also traditionally left in the toilet for him.
As can be seen self-evidently, the method performed by Sluzzle Dude is similar to the overnight deliverances of Santa Claus.
Unlike the joyful, more stylistic appearance of Santa Claus corresponding to Christmas, Sluzzle Dude is conceived to take on a more primitive appearance. This holiday figure is depicted to be a grey humanoid; he has green eyes, a beard, and a beanie hat; his attire also includes a black sweater, denim pants, and black shoes.