The Grouchketeers

"How can you tell a Grouchketeer? He's the one with the thumb in his ear!"

Like the Birdketeers, the Grouchketeers are a group of real kids dressed in costumes based on their leader, in this case Oscar the Grouch. Oscar depends on them to help him demonstrate things to the viewer (such as a game of Three of These Things), help him make things trashy or noisy, and sometimes even find him some more trash. Telly was a long-time Grouchketeer.