On the DVD commentary, the writer of this episode, Sera Gamble, says that The Breakfast Club (1985) was the inspiration for its plot (in both the movie and this episode, five disparate young people are trapped in a circumscribed space and learn about each other's lives and personalities).
Instead of the standard "Then" and "Now" recap, the show opens with "The Road So Far", just like in the last two episodes of season 1. This time, they show clips of all the special psychic kids the Winchesters have met along the way and the hints they've gotten about Sam's "destiny."
Sam finds himself in an old frontier town. This was actually the set for the 1989 TV series Bordertown (1989) which has featured in numerous TV shows and films since the series ended.
The fact that the boys' mother already knew Azazel is fully explained in Season 4.
Dean's signature on the receipt is "David Hasselhoff." David Hasselhoff is an actor best known for his roles in the 1980's TV shows Baywatch (1989) and Knight Rider (1982).