Mr. Monster appeared in the 1991 release Sesame Street Home Video Visits the Firehouse. A nice monster who always pays his rent on time, Mr. Monster roomed in Marge's attic. When a fire breaks out in the house, Mr. Monster has to be coaxed out and rescued by a firefighter, providing an object lesson in what to do when trapped in a burning building. Now rendered temporarily homeless, the monster is offered shelter by Big Bird, Elmo, and Gordon, but he misses his old dwelling and is relieved when a neighbor offers her attic, filled with the junk and dust he's accustomed to.
Both his voice and design are reminiscent of comedian Ed Wynn.