Episode 2.19, "Critical Film Studies" (aka, the "Pulp Fiction" homage)
"03/24/2011: JEFF PLANS A "PULP FICTION" STYLE SURPRISE PARTY FOR ABED AND THINGS DON'T GO EXACTLY AS PLANNED - Capitalizing on Abed's (Danny Pudi) love of cinema and pop culture, Jeff (Joel McHale) plans a very special "Pulp Fiction" style surprise party for Abed's birthday. The tables turn, however, and while the study group awaits their arrival at a restaurant, Abed stages another dinner with an unsuspecting Jeff at another restaurant. Chevy Chase, Gillian Jacobs, Alison Brie, Yvette Nicole Brown, Ken Jeong and Donald Glover also star."
Episode 2.20, "Pain Management Through Wine Tasting" (aka, the Pierce-centric & Abed's "Who's the Boss?" episode)
Episode 2.21, "Paradigms of Human Memory."
Sources: A B C