Parodies and psychology, meta humor and monkeys, laughs and tears
"Introduction to Finality" (Season 3, episode 22)
The end of the Harmon era, and judging by the way it was structured, he had a good idea it was coming, from either cancellation or non-renewal of his contract. A smaller-scale episode — albeit one where Evil Abed runs amok and Troy becomes messiah to Greendale's air-conditioning repair school — that provided big emotional breakthroughs for Jeff, Abed, Troy, Britta, Pierce and Shirley, that concluded with the study group closer than ever, and with a season-ending musical montage like the ones "The Wire" always used. If you believe that "Community" ended with Harmon's exit, then this functions perfectly as a series finale. And if you're willing to give the new guys a try, it still offers a clean break between one era and the next, rather than ending on some kind of Sorkin-style cliffhanger that Port and Guarascio will have to clean up later.