Sam tells Dean, "Fine. Then whatever the magic pill is, I'll take it too." To which Dean replies, "What is this, Sid and Nancy?" He is referring to Sid Vicious, singer and bassist for the punk rock band the Sex Pistols, and his drug-addled, destructive relationship with his girlfriend, Nancy Spungen.
When Sam tells Dean that the first victim's body was covered in someone else's bloody fingerprints, Dean says, "Okay, great. My man Dave Caruso will be stoked to hear it." He is referring to David Caruso who is best known for his roles in the TV crime dramas NYPD Blue (1993) and CSI: Miami (2002).
Terence Kelly, who plays the morgue doctor, played Daniel Elkins in the season one episode Dead Man's Blood (2006).
When Dean finds out that the fingerprints on the first victim are all of a man who has been dead several years, he asks Sam: "what are we dealing with, Walking Dead?" He is making a reference not to the popular TV Series, as the series didn't debut until 2010, more than two years after this episode even aired. Dean is in fact referencing the comic book source material of the same name, which has been in publication since October 2003. Jared Padalecki (Sam), Jensen Ackles (Dean) and Jeffrey Dean Morgan (John Winchester) have all been fans of the comic since it first began. Coincidentally, Lauren Cohan (Bella Talbot) has gone on to play the lead role of Maggie Greene on The Walking Dead (2010), since season 2, and as of the end of season 5 in early 2016, Jeffrey Dean Morgan has played the role of the infamous villain Negan, a role he was thrilled to get as a fan of the comic.