The bar keeper in the saloon is named Elkins. In season 1, Dead Man's Blood (2006), the boys meet a Daniel Elkins who possesses the colt. It's likely that the bar keep is an ancestor of Daniel Elkins, and the colt remained in the Elkins family until the vampires took it from Daniel.
Dean introduces Sam as "Walker, he's a Texas Ranger", which is the name of the TV series Walker, Texas Ranger (1993) starring Chuck Norris in the title role. Jared Padalecki stars in the title role in the reboot Walker (2021) for the CW.
Bobby (Jim Beaver) mentions that the only Star Trek incarnation he is familiar with is Deep Space Nine. Beaver's late wife, Cecily Adams, played the recurring character Ishka on Star Trek: Deep Space Nine (1993). Additionally, Beaver played Adm. Leonard in the first episode of Star Trek: Enterprise (2001).
The gold Sam and Dean take to Wyoming is the gold they took from the dragons in Like a Virgin (2011).
Dean goes by Clint Eastwood, like Marty did in Back to the Future Part III (1990). Even wearing a serape.