Timmy Monster appeared on "The Muppet Show", and was performed at various times by Steve Whitmire, Dave Goelz, and late Jim Henson.

Timmy is a full-bodied blue-green monster. He first appeared in the background during the opening of the Ben Vereen episode, and later joined Ben Vereen in the closing number, "Pure Imagination."

In the Ben Vereen episode, certain publicity photos, and the cover of the first Muppet Show album, Timmy had green hands, eyes without eyelids, and what appear to be goggles or antennae over his eyes. From the second season onward, he lost his eye antennae and gained eyelids and green hair. Later in the second season, his hands were changed to match the color of his fur, he lost his hair, gained teeth and a tail, and his eyes and eyelids changed.

Timmy's name was mentioned in the Carol Channing episode, in which he stretched a pair of too-small shoes for Miss Piggy. Steve Whitmire performed him in this scene.