Alex Hirsch has been insinuating in his tweets for the past few weeks that last night's episode of Gravity Falls was going to be a big one. He didn't lie.
"Dipper and Mabel Vs. The Future" began by tugging at our heartstrings and then ended with completely yanking them apart. With the Pine twins' thirteenth birthday only a week away, Mabel is determined tho throw the best birthday bash Gravity Falls has ever seen. Meanwhile, Dipper and Ford embark on a mission to seal the interdimesional rift, using an extraterrestrial adhesive located in a giant UFO hidden under the town. As Mabel finds out that none of her friends can attend her party and growing up is nothing but bad, Ford offers Dipper the opportunity to stay in Gravity Falls to be his apprentice. Mabel overhears Dipper accept his invitation and, realizing she has just lost the only thing she has left, breaks down. All she wants is for things to stay the way they are.
This is far from the first time we've seen Mabel worrying about she and Dipper drifting apart like Stan and Ford. So when she was given the opportunity to save their relationship, she took it - even if it meant unknowingly starting the apocalypse. After fleeing into the woods, she is confronted by the time-traveler Blendin (yes, because he blends in). He offers to place Gravity Falls in a "time bubble" - something that will make summer last forever, and thereby allowing Mabel to keep things as they are. In return, he asks for the rift. After finding it in Dipper's backpack that she conveniently/accidentally took, she hands it over. It is then that Blendin smashes the rift - which, according to Ford, will unravel reality itself - and reveals himself to be none other than Bill Cipher. With a snap of his fingers, Mabel collapses and a giant interdimensional hole opens up in the sky. As Ford says just before the episode's end, "It's the end of the world."
Fans have already taken to the internet to discuss theories on the ever-present hidden secrets of the episode, one of which involves Blendin. In "A Tale of Two Stans," another one of this season's biggest episodes, the phrase "BLENDIN WAS HERE" is written on a board by the beach in Stan and Ford's flashback to their childhood. What was Blendin doing there, and what does that have to do with last night's episode? As fans have also pointed out, one of the locations that can be seen on Blendin's jumpsuit as he approaches Mabel in "Dipper and Mabel Vs. The Future" looks suspiciously like school that teenage Stan and Ford attended. The same school where Stan supposedly broke Ford's science fair project - the catalyst that ended up driving them apart. However, although Stan did mess with his brother's project, he never actually broke it. So who did?
Blendin. Or, more specifically, Blendin under Bill's possession (Billendin?). With the graffiti and the location on his jumpsuit, it's more than obvious that he was there. Therefore, the theory goes on to speculate that Bill used Blendin to make sure that Stan and Ford were driven apart so that, decades later, Mabel would desperate enough to do anything to make sure she and Dipper didn't become like them. Billendin made sure that the backpacks would be switched so that when he met Mabel in the forest (how else would he know exactly where she was going to be?) she would be desperate enough to give him the rift, therefore completing his plan that was years in the making. This would mean that all the events of the series as we know them exist in an alternate timeline, and that the correct timeline may be one where Stan and Ford were never driven apart, and everything is be completely different.
So now what will become of Gravity Falls? If the chilling end credits scene is indicative of anything, it doesn't look good. Far-off screams and sirens can be heard as a flyer for Dipper and Mabel's part lies discarded on the ground before blowing away. As always, the episode ends with a coded image card; this one being a poem of sorts:
"THE PROPHECY SEEMED SO FAR AWAY
BUT FINALLY WE’VE REACHED THE DAY
GIVE UP THE PAST. EMBRACE THE STRANGE.
EVERYTHING YOU CARE ABOUT WILL CHANGE"
The promo for the next episode (which can easily be found all over the internet, at this point) makes it clear that Bill is collecting people for his infamous circle. What will happen when he gathers them all? Will Mabel wake up? Is this truly the end for Gravity Falls? And why is Soos's grandmother an armchair? Unfortunately, we have to wait until October 26 to find out. But one thing's for sure: Bill now exists in reality (he's missing from the famous Cipher Wheel that flashes on screen from a fraction of a second), which can't mean anything but bad news for Dipper, Mabel, Stan, and everyone else in Gravity Falls.