And somehow… the love meme lead to me rewatching Friday the 13th (2009)! Which is excruciatingly boring! Here is the most interesting summary I could drum up while I was waiting for it to end. Bear in mind that I was narrating this as I went, but as the film progressed (particularly toward the end, when Sam and Dean reunite) it just got more and more perfect. Man, I didn't even have to try. XD
2009, 4x21 alternate timeline.
The Winchesters never reunite after Sam leaves the penthouse to kill Lilith and Dean leaves that doctored voicemail. The Seals break and the Apocalypse still starts, but they get caught in an unusual crossfire that leaves them unarmed, mentally rattled--and in Dean's case, genderswapped. Why? Uh, who knows. Heaven works in mysterious ways. Anyway, the film begins when Sam, having tracked Dean to a cabin on Lake Chitaqua, gets caught up in having to save some exceptionally dumb civilians. (Sam is at this point traveling by road bike, since Dean has the Impala. When he goes missing, the police assure him there was no left car. But even with the Impala vanished, Sam refuses to believe Dean's dead.)
Sam eventually locates Dean, and together they wrest victory away from Jason by suitably violent techniques: Dean distracts him by confronting Jason about his mommy issues, giving Sam the opportunity to do god knows what with a bear trap. Dean condemns the killer, Jason--to Hell, to join his mother--before dealing the finishing blow. This is a critical rhetorical moment, given Dean's struggle with his own relationship with Hell this past year, and his own mommy issues (because John has been posthumously genderswapped as well). When he stabs Jason in the chest, he establishes an identity between him and Jason, because, well. He's familiar with Hell, and he's a killer too.
Then Sam and Dean dump Jason's body in the lake and have an emotive tag scene on a dock--the cinematic successor to their dock scene in 4x08. But where Dean refuses to discuss Hell with Sam in 4x08, an unexpectedly revived Jason breeches under the dock, grabs Dean, and drags him down with him--both are Hellbound. Afterwards we just skip over S5/6/7/8/9 and go straight to demon!Dean in S10, I guess?
Obligatory SPN!goggles aside, that is… actually a pretty accurate summary of the film! I mean, when not-actually-Sam describes his home life to the civilians he's supposed to be saving, he even talks about leaving when he was 17 and his sibling choosing to stay with their mother. AND THEY USED TO BE CLOSE, BUT LESS SO NOW, AND THEY HAD A FIGHT, and…
Well, anyway, if you like your Sam sibling-searching and sitting around in a cabin in the woods, you could watch this movie. Alternatively, you could just rewatch S4, wherein Sam is sibling-searching and also sitting around in a cabin in the woods: