Bobby (Jim Beaver) says to the Sloth Demon, "Fat, Drunk and Stupid is no way to go through life, son". This is a famous line from National Lampoon's Animal House (1978).
At the beginning of the episode, Sam is researching for possible ways to get Dean out of his deal. One of the pages refers to the German legend of Faust. According to the legend, Faust was a highly accomplished scholar who is bored and/or unsatisfied with what he has accomplished. He makes a deal with the Devil's servant Mephistopheles for unlimited knowledge and worldly pleasures in exchange for his soul. As a condition to the deal, after a set period of years, the Devil/Mephistopheles will collect Faust's soul and he will be eternally damned.
The Envy Demon says, "I am Legion, for we are many." This is a quote from the New Testament of the Bible (Mark 5:9) where Jesus -- while performing an exorcism -- asks who is inside of the man and it answers that the guy is filled with demons.
The Chevy Chevelle Bobby is driving is the same one that the vampires drove in the episode Dead Man's Blood (2006); season 1 episode 20.
The title of this episode is from the Yul Brynner/Steve McQueen classic film The Magnificent Seven (1960).