The interesting thing about cataloguing pop cultural references from a referential show that ran for 15 season is watching the references start out very Gen-X ("Gilligan's Island," "The Dukes of Hazzard"), hit a millennial high (iPods, so much "Twilight") and go out with a tinge of Zoomer (Baby Yoda, "Sir, this is an Arby's.").
This list happened because seasonal depression, a lot of downtime, and the 20th Anniversary of SPN's Pilot looming in September. The rules are...there are no rules. Okay, a few rules: what I considered "references" were either included in dialogue (the majority of them), episode titles, onscreen reading material IF the reading material exists in the real world, onscreen media IF the media exists in the real world, mythological figures IF they have a real world basis (and I was not consistent with this one, sorry). Music was only included if it was a) an episode title, or b) the lyrics were sung or spoken by the cast. Enjoy clicking!