Dean, Castiel, Sam, and Jack use the aliases Russell, Kilmer, Elliott, and Paxton, respectively, all of which are actors from the movie Tombstone (1993).
The title of the episode is based off of the film Tombstone (1993), which recounts the shootout at The O.K. Corral between lawmen Wyatt Earp and Doc Holliday and a group of outlaws, who are also referenced throughout the episode.
While Dean is crawling through the tunnels underneath the graveyard, he paraphrases John MacClane's line while crawling through the air vents in Die Hard: "Sure. Come to Dodge City. We'll have some laughs."
"Two salty hunters, a half-angel kid, and a dude who just came back from the dead... again. Team Free Will 2.0, here we go!" is said by Dean in the bunker. This echoes an earlier line, "one ex-blood junkie, one drop-out with six bucks to his name, and Mr. Comatose over there" from season 5 when Dean coined the term "Team Free Will" to mean those fighting against the archangel Michael.
First appearance of Castiel's new trench coat.