In the beginning scene, when the young girl is with the vampire at the bar, the vamp calls her Kristen, and later in the alley, she calls him Robert. This is a reference to the vampire-human couple in the Twilight (2008) movies, played by Kristen Stewart and Robert Pattinson.
While trying to guess the victim's password, Sam starts to ask, "How many Ts in 'Pattinson," before his attempt works. This is a reference to Robert Pattinson.
While trying to guess the password to the missing girl's laptop, Dean suggests "Lautner" and Sam replies "he's a werewolf". This is a reference to Taylor Lautner who portrayed a werewolf's character in the Twilight (2008) film series.
"Boris" says something to the effect of "they've turned us into Prince Charming with a Volvo." Edward Cullen, in both the Twilight books and movies, drives a Volvo, specifically an S60R in the book and a C30 in the film, both silver.