Troy says that he is a Jehovah's witness. In real life, Donald Glover grew up as a Jehovah's witness.
At the beginning of the episode when the cast is discussing their respective religions, Britta asks Pierce if he's sure he's not in a cult, to which he replies, "Just by asking me that you've put me back down to a level 4, you now owe me 2000 Energon cubes". Energon is the primary power source for the Transformers franchise, often depicted in cube form.
Folks are bringing food to Shirley's 'Christ uber alle' party and she says, 'Oh, hash browns and applesauce, that's nice'. Annie has brought potato Latkes with sour cream and applesauce, perhaps the most traditional of all Hanukkah treats.
While the guys are having lunch, Pierce says regarding Anthony Michael Hall's character "I know guys like this Mike, used to be a nerd now he's a meathead." Chevy Chase (Pierce) worked with Anthony Michael Hall in National Lampoon's Vacation (1983), and in numerous 80s John Hughes films (National Lampoon's Vacation, Sixteen Candles, The Breakfast Club, & Weird Science) Anthony Michael Hall was repeatedly cast as a nerd, but bulked up and was eventually cast in more muscle head, bully type roles (Johnny Be Good, Psych, and now this role in Community).
In real life, Danny Pudi is Roman Catholic.