Dean has a code word for when he is in trouble and a gun is being held on him, "Funkytown."
In an extended scene, viewable on the DVD but cut from the final episode, just before Sam asks Ash for help finding other psychics, Ash is unsuccessfully hitting on a woman. As she walks away from him, he yells to her back, "Gimme some sugar, baby!" This is a much-loved line from Army of Darkness (1992), in which it is also spoken by a demon-hunting character named Ash.
"Funkytown" is only used in this one episode, Sam and Deans real code word for trouble is "Poughkeepsie" even used later in the series by Crowley.
Tom McBeath (Mr. Carey) comes back in S9 E7 Bad Boys (2013) as Jack (a victim) at the boys home where Dean spent some time as a teen.
Lafayette, IN is in fact a real town, next to West Lafayette, home of Purdue University. Furthermore, there is indeed a Monroe street that goes through it.