u/Smokagon

This might be already mentioned but I love how many subtle references from older episodes are in this show. The latest one I caught on now after a billion rewatches is the one in s01 e09 where Troy asks Abed if he is going to cry again because he accidentally listens to Come Sail away by Styx. A cover of this song is used in s05 e05 when Troy actually leaves the school on a boat with LeVar Burton who would be the obvious reference everyone would catch on right away.
I just love how small details keep popping up while rewatching over and over again.