12. Cooperative Calligraphy (Season 2, Episode 8)
For those unacquainted with the term, a "bottle episode" is a segment of a TV show or movie that is filmed entirely in one room, with only the most important cast members (see Hitchcock's Rope, or Doctor Who's The Edge Of Destruction). Cooperative Calligraphy is Community's version of a bottle episode. The story begins with the Greendale Seven's study period ending, and they're about to either go home or attend a puppy parade on Greendale's campus. But the moment before they step out the door, Annie Edison realizes her purple pen is gone, and asks if anyone has seen it. No one has, and they attempt to leave once more. But Annie is convinced someone has been stealing her pens, since numerous pens of hers have disappeared before. She keeps bringing purple pens, and someone keeps taking them. Therefore, anger amongst the group keeps boiling, until finally they look the room down and search every corner of it, then search each other to see what's become of the pen. The truth is eventually uncovered at the end, and I guarantee none of you saw it coming. The episode is a key development in season 2's story, and is required viewing even if you're not watching the episodes in order.
Best line: "I hate bottle episodes. They're wall-to-wall expressions and nuance. I might as well sit in a corner with a bucket on my head."
11. Epidemiology (Season 2, Episode 6)
Community, ever ready to parody film and TV tropes, decided it was time to bring on zombies. Not just in a character's dream, not just students messing around, but having the school actually get overrun by hordes of living zombies. The episode closely follows (as usual) the Study Group as they hide out in the library and try to avoid getting bit. Unfortunately, one of them already has, and she's locked in the room with them, forcing them to flee and find a new hiding place. Eventually, they discover the source of the zombie plague, and find out to reverse it, they must simply lower the temperature in the school to a low, low heat. The episode then follows them as they try to find the master thermostat, and attempt to survive as one by one, the study group gets bitten and falls away.
Best line: "Heavens Annie, what big fists you have.... in your face!"