From the cartoon, Hey Arnold!
Fuzzy Slippers is Gerald Johanson's mysterious informant, who provides him with urban knowledge of a wide variety of subjects, including urban legends and advice about local people. We never do see Fuzzy Slippers throughout the show, and only hear reference to him from Gerald.
Gerald: "See Arnold, I told you, Frankie G is bad news; Fuzzy Slippers tells no lies man."
Arnold: You're a bold kid Gerald, a bold kid.
Gerald: Wait a minute, that's my line.
Arnold: Oh yea.
Gerald is the keeper of the tales of the urban legends, which he has learned from Fuzzy Slippers. The urban legends include: Wheezing Ed, Stoop Kid, Pigeon Man, Big Caesar, Monkeyman, and Ghost Bride.