The Muppets are a group of puppet characters created by Jim Henson. Individually, a Muppet is one of the puppets made by Jim Henson or his company's workshop. Although the term is often used to refer to any puppet that resembles the distinctive style of The Muppet Show, the term is both an informal name and legal trademark linked to the characters created by Henson.
The word "Muppet" itself was said by Henson to have been created by combining the words "Marionette" and "puppet". However, Henson was also known to have stated that it was just something he liked the sound of, and he made up the "marionette/puppet" story while talking to a journalist because it sounded plausible.
Barry proclaims that there is a person inside of Big Bird in "A Piñata Named Desire".
Snot shows up at the hospital where Hayley has severe kidney damage with his Fozzie Bear puppet and attempts to cheer up Stan and Francine in "The Kidney Stays in the Picture" but reveals he's really there because his grandmother is dying.
Steve makes a booby-trap out of a collection of Muppet dolls in "Toy Whorey".