When Dean shows Sam his game with their mother, his letters are an anagram for Lucifer. However, when the screen is partially shown in the previous shot, different letters are visible.
In the backstage scene, before the reunion show in club Meteor, one of the dead band members has changed position and can be seen blinking.
Dean is adamantly against hair metal yet he listened to RATT & Quiet Riot and Bon Jovi earlier in the series.