The Muppet character who is the janitor on The Muppet Show is Beauregard.
Beauregard works backstage at the Muppet Theatre as a janitor and stagehand. He is well-meaning but dim-witted, and his attempts to help frequently create accidental chaos. Rather than seeking the spotlight, he is generally more comfortable handling props, cleaning, and backstage tasks.
The character debuted during season three of The Muppet Show and was performed by Dave Goelz. Beauregard sometimes wanders onto the stage while still doing his job, only realizing afterward that he has interrupted a production. His characteristic slow reaction and quiet “Right” became part of his comic identity.
Beauregard also appeared in The Great Muppet Caper as a taxi driver and later took other supporting roles, including engineer of the Muppets’ tour train in Muppets Most Wanted. He is sometimes confused with George, an earlier Muppet Theatre janitor, but Beauregard is the named janitor most strongly associated with The Muppet Show’s backstage crew.