When Dean tells Garth that he has been in Purgatory, Garth asks "Like Purgatory, Purgatory?" Then Dean responds "No, the one in Miami." To which Garth responds "That's balls!"
The Purgatory in Miami is a Gay strip club.
Chilton Crane who appears in this episode as "Mary Lew" has previously appeared in Supernatural. In season 2 Crane portrayed Beverly Tanner in the episode Croatoan (2006).
Garth's cover is as a Texas Ranger and he is going by the name "Ranger McCrae" which is a reference to the main character of Larry McMurtry's best selling novel and acclaimed TV mini-series, Lonesome Dove (1989). Captain Augustus McCrae was a retired Texas Ranger and was played by Robert Duvall in the mini-series. The story follows retired Texas Rangers Gus McCrae and Captain Woodrow Call, played by Tommy Lee Jones, as they drive a heard of 2,000 head of cattle from south Texas up to northern Montana.
The Confederate Tomb of the unknown soldier is in Biloxi, Mississippi. Kearney, Missouri does not have one. Kearney is most famous for having the birthplace of Jesse James. The original house still stands & is quite a popular tourist destination.
Garth tells Sam and Dean "even if there was any sulfur, Barney Fife and his crew probably contaminated the whole crime scene and any evidence that was here with it." He is referring to the bumbling deputy sheriff from The Andy Griffith Show (1960).