Katie McElhenney (Rob McElhenney's sister) is one of the girls who screams "pervert" and "dickhead" to Glenn Howerton at around 4:45 mins.
Charlie is seen wearing a Bayside Tigers shirt, which is another reference to Saved by the Bell (1989). During the season 1 episode Charlie Got Molested (2005) the gang believes Charlie was molested by a former teacher. This teacher was played by Dennis Haskins, most famous for his portrayal of Richard Belding on Saved by the Bell.
Charlie's mom's extra blush during the dinner scene is a nod to Lynne Marie Stewart's role as Miss Yvonne in The Pee-Wee Herman Show (1981).