FOXGetty Images For a school in a small Ohio town, William McKinley High sure did see more than its fair share of celebrity visitors over Glee's six seasons. The musical comedy/drama made viewers wish they could sing and dance their way through their lives. And the list of fans of the show—a.k.a. Gleeks—included many Hollywood stars that *also* wanted the chance to belt some truly fabulous songs. Over the show's full run, Academy Award winners, Tony Award winners, Grammy Award winners, and one EGOT recipient (All hail Whoopi) stopped by to perform their hearts out with Rachel, Mr. Shue, Kurt, Santana, Brittany, and the rest of the gang. Some you may remember and some may have you saying, "Wait, how did I miss this?!" And it's more than likely that at least one will have you looking up a clip of their performance.