S2, E21: As The School Year Draws To A Close The Study Group Reflects On Their Favorite Memories From The Past Year In Never Before Seen Flashbacks – As The Study Group Gathers To Assemble Their 20Th And Final Anthropology Diorama Of The Year, They Begin Reminiscing About Their Favorite Times Together – Including A Trip They Made To A Western Ghost Town, A Last Minute Glee Club Performance And The Array Of Costumes That Dean Pelton (Jim Rash) Has Managed To Wear Over The Year. Meanwhile, Troy’S (Donald Glover) Pet Monkey Returns, Only To Disappear Back Into The School’S Ventilation System. Joel Mchale, Gillian Jacobs, Chevy Chase, Alison Brie, Yvette Nicole Brown, Danny Pudi And Ken Jeong Also Star.