Sam was given a shoulder injury in the series after Jared Padalecki dislocated his shoulder wrestling with Osric Chau (Kevin) at a convention the previous summer.
At a convention, Mark Sheppard (Crowley) said the only reason Dean was singing "I'm too sexy" at the karaoke was because the show couldn't get the rights to "All by myself". He then joked that when there's a song on the show, it's usually the crews third choice.
Crowley and Dean's exchange of "Jerk, Bitch", is a throwback to Sam and Dean's teasing exchange of the same in Pilot (2005); repeated throughout the earlier seasons.
Dean sings karaoke throughout the episode and is booed for singing poorly. In reality, Jensen Ackles is a singer and guitar player and has sung at multiple conventions and even released an album entitled 'Vol .1' with Steve Carlson under the band name Radio Company in 2019
Giacomo Baessato, the actor that played the angel Daniel, was also the pizza delivery guy in S04E05 Monster Movie (2008).