This is by no means a comprehensive list. To do that I'd have to re-watch every episode, meticulously taking notes every time a movie reference came up. I'd also have to write down everything that sounded like a movie reference, even if I didn't recognize it, then go on Google and search for the movies that the mystery references came from. I didn't do that, so I have an incomplete list. If anyone knows of any reference that I've missed, please let me know in a comment.
Poltergeist--mentioned briefly in the episode "Phantom Traveler". I naturally mean the original, not the remake. If you want to watch the remake, fine. It's a good movie as remakes go, but watch the old one first. And if, heaven forbid, you've seen the remake but not the original, then drop whatever you are doing and go watch it right now.
The Sixth Sense--mentioned in "Asylum" when Dean calls Sam "Haley Joel".
Deliverance--Mentioned briefly in "The Benders".
It--I don't remember if there are any direct references, but "Everybody Loves A Clown" is about an evil clown. You can't really know the evil clown genre until you've seen It.
Star Wars--Okay, I know, there are two kinds of people in the world: those who have seen Star Wars and those who are very proud of their identity as Someone Who Has Not Seen Star Wars. But still. If you watched the episode "Simon Said" and didn't quite get Dean's line, "He freakin' Obi Wanned me," then just go watch Star Wars. Please.
The Exorcist--If you're a horror buff, which you must be if you're watching Supernatural, then you should have watched this movie long ago. But if you haven't, now's the time. The episode "The Usual Suspects" stars Linda Blair, and while it's actually pretty light on Exorcist references, there are a couple.
The Shining--The episode "Playthings" is basically one long tribute to this movie.
The Evil Dead--In "Hollywood Babylon" Sam and Dean visit a movie set. The movie being made is very similar to The Evil Dead. Again, please watch the original, not the remake.
Groundhog Day--Lot's of shows have done tribute episodes to this movie, and Supernatural is no exception. Before you watch "Mystery Spot", watch Groundhog Day.
Back to the Future--In the episode "In the Beginning", Dean goes back in time and meets his parents. Need I say more?
I Know What You Did Last Summer--Again I don't remember if there are specific references to the movie itself, but a season four episode has this title, so you might as well watch it.
The Omen--"I Believe The Children Are Our Future" is about the antichrist, so why not watch this classic movie on the same subject.
Stay Tuned--I haven't seen this movie in years and remember very little about it, but the episode "Changing Channels" seems to be loosely based on it.
Ghostbusters--Lends its name to the episode "The Real Ghostbusters", but referenced in other episodes as well. If you like the horror/comedy genre, which you must if you're watching Supernatural, but haven't seen this movie, go watch it right now.
Girl, Interrupted--Lends its name to the episode "Sam, Interrupted."
My Bloody Valentine--this time if you want to watch the remake (starring Jensen Ackles) then go ahead, but if you're a true movie nerd you'll watch the old one too.
Weekend at Bernie's--lends its name to the episode "Weekend at Bobby's".
Twilight--yeah, I know, you wouldn't be caught dead watching that movie. But if you really want to understand the episode "Live Free or Twihard", then bite your bottom lip and just do it. It will only take a couple of hours, I promise.
A Beautiful Mind--mentioned a couple of times in reference to Sam's hallucinations.
Misery--referenced somewhat in the episode "Season Seven, Time for a Wedding".
Black Swan--mentioned in the episode "Out With the Old".
The Lord of the Rings Trilogy--also from "Out With the Old". The ballet shoes in this episode change size to fit the wearer, and once someone has touched them they have an overwhelming urge to put them on.
The Ring--I don't remember the episode, but I know Sam mentions this movie at one point.
We Need to Talk About Kevin--lends its name to the first episode of the season.
Lars and the Real Girl--lends its name to the episode "LARP and the Real Girl".
Dog Day Afternoon--inspired the title of the episode "Dog Dean Afternoon".
Paper Moon--lends its name to an episode in this season.
Night of the Living Dead--The first two episodes of this season borrow heavily from the zombie genre, so you might as well watch this classic.
The Bad Seed--lends its name to the third episode of the season.
As I said, this is an incomplete list. If you have anything to add, let me know in a comment.
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