The character of Dwayne is obviously a big fan of 1980's thrash metal. The shirt he wears for the majority of the film, is the album cover from Metallica's "Master of Puppets" (1986). Additionally, Dwayne's ringtone is "Raining Blood" by Slayer from their album "Reign in Blood" (1986).
When Nick (Jesse Eisenberg) is talking to Kate (Dilshad Vadsaria) for the first time, it is mentioned that he doesn't have a Facebook account. Nick states that he is "off the grid". Eisenberg also played Mark Zuckerberg, the founder of Facebook, in The Social Network (2010).
Fred Ward is credited as The Major, but near the final third of the film, when he is walking through his house, his oversized lottery check is shown on the wall, issued to him. So, his character's name is Major Jerry Mikowiski.
It is suggested that the character of Travis (Nick Swardson) may be a "Juggalo" (the name for fans of the Detroit rap duo Insane Clown Posse). This is implied by the fact that in some scenes he is seen wearing a Jersey bearing the logo from their album Bang! Pow! Boom! He also has a release poster from that same album that can be seen in the background of Travis' room.
When Dwayne gave the signal to bring Kate out from their van, Travis said that he took so long getting out because Kate knocked over his "SODA." The film takes place in Grand Rapids, Michigan, any real Michigander would call soda "POP."