Mad Man Mooney appeared in The Muppet Movie as the owner of "Mad Man Mooney's Hubcap Heaven", a used car dealership. It was there where the Muppets first met Sweetums, who worked as Mad Man Mooney's "Jack". Mad Man Mooney was a bit of a con man; When a fender fell off of one car, he claimed that they were removable for narrow garages. His policy includes a twelve dollar trade in for all used cars, and the prices that customers see on the car is the price that they pay.
Mooney is referenced in The Muppets, where Sweetums is shown to be working for him again (the dealership now named "Mad Man Mooney and Sons").