The Question
From Muppet Wiki
The Question, similar in design to the Balloon-Head Conductor, is a tuxedo-clad character with a pink balloon for a head. The Question's balloon head appropriately has a big question mark where its face should be.
In the At the Dance sketch on The Muppet Show episode 115, George the Janitor asks Mildred if he can pop The Question, and then he does.

