The Grouchketeers are a group of real kids dressed in costumes based on their leader, 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.
One of the group's earliest meetings was held in Episode 1118 for the purpose of "making little grouches a little smarter". An appearance in Episode 1952 featured Grundgetta leading a Grouchketeer meeting and playing "Cross it Out." Grundgetta calls the kids up and asks them to cross out a different thing on her card. David calls her out on something; the kids are good at crossing things out, but she's done nothing. She gets the card and crosses the whole thing out.
The club was last featured during season 38.