While Sam is going through Gary's box, there is a copy of Busty Asian Beauties. Same magazine Dean got at the gas station in episode 1 of season 4 Lazarus Rising (2008).
Entering the basement to hunt for the witch's bones, Gary is carrying a shotgun and says "Booyah, Master Chief is in the house". Master Chief Petty Officer John-117 is the main character in an enormously popular and successful online First Person Shooter game Halo: Combat Evolved (2001).
Sarah Drew plays Nora, Gary's friend. She also has a role on Grey's Anatomy (2005) which the boys mock in season 5 episode 9, Changing Channels (2009), as well as Jeffery Dean Morgan ,who plays Sam and Dean's father, played a role in seasons 2, 3, and 5 of Grey's Anatomy.
The Latin incantation Gary uses to summon the demon is: "Attenrahendum eos ad ligandum eos patiter et solvendum et ad congregantum eos coram me". Which very roughly translates to "We must attend them to bind them patiently and must be solved and to gather together them before I".