Fred is a large, green, dragon-like monster. He debuted as a nameless father monster in the sketch "Monster Father and Son" on "The Ed Sullivan Show", with Baby Monster as his son. The character subsequently appeared on "Sesame Street", where his name was mentioned in a Season 1 sketch by the character who would become Grover.
In some "Sesame Street" appearances, his teeth were not visible. In one skit, in which Ernie goes rock hunting, he also had a large rock-like dome instead of horns.
He also appeared in the background in "The Great Santa Claus Switch".