Posted this at 5/8, so might as well here. Kudos if you get it without any hints:
"The Politics of Human Sexuality"
Air Date: December 3, 2009
"The Psychology of Letting Go"
Air Date: October 7, 2010
Holy shit.
... not getting it.
It's an extremely in-joke, but here we go:
In "The Politics of Human Sexuality", there's a barely-there joke about the condoms the dean was handing out being defective, and he tells Abed to warn the entire school. He opts to say something along the lines of "The condoms are broken, so if you must have sex tonight, please don't use condoms".
In "The Psychology of Letting Go", there's an entire subplot that takes place without any dialogue, only in the background, of Abed befriending a pregnant girl who then gives birth later in the episode.
Sure, it's about a month late, but hey, I was a big baby and came three weeks late, so it's not unheard of. Anyway, it's an amazing joke for people who really dissect the episodes. Possibly even better than Abed's Robocop memos and Decision Gate's crawl put together.