When Ice T (played by Dan Harmon) returns to save Earth, he says "I care now!" This line is taken verbatim from the animated end segment of the Community episode 2:21 "Paradignms of Human Memory".
Birdperson appears and is still dating Tammy from this episode
Morty teleports to the same butt world that appeared in this episode.
"Get Schwifty" is #10.