Trapped in the apocalypse and menaced by villains new and old, Dipper finds himself in a race against time.
The episode opens up right where the previous one left off, with Bill Cipher laughing at the gateway between the Nightmare Realm and Gravity Falls. His body gains flesh, metal, and pure energy as Bill finally obtains a physical form, becoming a triangle of light.
Blendin Blandin sees the carnage above, and is helpless to watch as Mabel's unconscious body is lifted up and sealed in a pink bubble emblazoned with a shooting star. Chains wrap around the bubble, sealing Mabel inside. Blendin taps his wristwatch, informing the Time Paradox Avoidance Enforcement Squad of the situation before teleporting away.
The townspeople of Gravity Falls look up to the sky in fear as Bill grows in size, becoming a rotating pyramid-like abomination with six arms and a pure black form with multicolored energy. Bill returns to his normal form and floats down to the town, announcing that he will be the lord and master of Gravity Falls for eternity. He then melts a statue of Nathaniel Northwest as the townspeople watch in despair.
Bill then introduces the town to the other residents of the Nightmare Realm that Bill calls his friends, each more grotesque and anomalous than the last; 8-Ball, Kryptos, Xanthar, Teeth, Keyhole, Hectorgon, Amorphous Shape, Pyronica, Pacifier, and many others. Their appearance is a floating single eye ball with 2 bat wings presumably. The townspeople don't react kindly to the display, urging Bill and his friends to get out of town. Preston Northwest offers to join Bill and become one of his "horsemen of the apocalypse", but Bill switches all the body parts on Preston's face instead. Bill then promptly unleashes his other minions and madness bubbles all over town that petrify, abduct, and instill insanity in the people of Gravity Falls. He also summons a gargantuan black pyramid from the ground to serve as his castle, and animates the Gravity Falls water tower. After proclaiming that time is dead and meaning has no meaning, Bill welcomes one and all to Weirdmageddon.
Meanwhile, Dipper and Ford watch the carnage from the Mystery Shack, their solitude interrupted by a flock of birds passing overhead. Many more animals, including the gnomes and a Manotaur, follow suit, knocking Dipper over. Ford picks him back up and telling him that with every passing minute, Bill's dimension leaks into theirs and his power grows. Dipper realizes that the interdimensional rift must have opened in Mabel's hands, and he runs off to go find her, trying to contact her through walkie-talkie.
Ford stops Dipper, telling him that before they can find Mabel, Bill must be stopped. Their best shot is to knock him back into the rift from where he came before Weirdmageddon spreads across the entire world. Ford isn't sure if it's even possible, but they have to try. The two abruptly stop when a gnome announces that a "weirdness wave" is headed their way. Dipper and Ford rush inside as a giant pink tsunami rushes over the entire town.
The weirdness wave spawns a tentacle in Soos' backyard, and it turns Abuelita into a chair. Soos is shocked by the tidal wave of madness, but Abuelita urges Soos to go help the others around town. Soos follows her order and heads off. Meanwhile, Stan is telling off Gompers for chewing on his fez's tassel. The weirdness wave causes Gompers to grow past the treetops of the forest, and Stan runs away with Gompers in pursuit. Next, it washes over the arcade, resummoning Rumble McSkirmish and also bringing other arcade characters to life.
Ford and Dipper go to the church, where Ford brings out his Quantum Stabilizer. He attempts to shoot Bill, however, he misses and is turned to gold and is toyed with. Dipper, enraged to see that his uncle has been turned into a golden backscratcher, decides to face to face with Bill as he tries to find something in the journals to defeat Bill, but he hesitates and tries to punch him. Bill forces Dipper back and destroys the journals. Bill then commands 8-Ball and Teeth that they two can have a treat, and that would be eating Dipper alive. While Bill and his other friends ride the Ferrari, Dipper successfully flees to a safe spot before he could be eaten by the two threats.
He runs into the mall in hopes of finding other survivors. The mall is all torn up and broken but he sees some nachos on a table goes over to have a snack. The nachos were actually a trap set by Wendy, who had been hiding out in the mall with Toby Determined. Wendy says that every Christmas instead of celebrating they practice to survive the apocalypse and says its pretty cool it actually paid off. She shows Dipper her hideout and they go on the rooftops to find Mabel. Dipper realizes Mabel is in the pink sphere with her shooting star on it.
They devise a plan and runs to the abandoned car store. Suddenly they are stopped by 3 cars. It turns out Bill Cipher had made Gideon Gleeful the sheriff of the wastelands. Gideon shows off that he has the only key to Mabel's Sphere but Wendy manages to escape with Dipper into a car. They have a chase and they crash. They meet up with Soos but Gideon easily catches up. Dipper convinces Gideon saying if he attack Bill, he could be seen as a hero in Mabel's eyes and thus Mabel could love Gideon. Gideon agrees and runs off with his prison gang to defeat Bill.
Dipper, Soos, and Wendy make it to the sphere, they open it up and go inside which then the screen fades to white with "To Be Continued" written on it.
- Directed by:
- Additional Written Material by:
- With the Voice Talents of:
- Jason Ritter as Dipper
- Alex Hirsch as Grunkle Stan and Soos
- Louis C.K. as The Horrifying Sweaty One-Armed Monstrosity
- J.K. Simmons as Ford
- Will Forte as Tyler Cutebiker
- Danielle Fishel as Pyronica
- Patrick McHale as Hectorgon
- Andy Merrill as Teeth
- Brian Bloom as Rumble McSkirmish
- Jennifer Coolidge as Lazy Susan
- Carl Faruolo as Grenda
- Jackie Buscarino as Pacifica Northwest
- John DiMaggio as Manly Dan
- Nathan Fillion as Preston Northwest
- Linda Cardellini as Wendy
- Kevin Michael Richardson as Sheriff Blubs
- Justin Roiland as Blendin Blandin
- Thurop Van Orman as Li'l Gideon
- Dave Wittenberg as Time Baby
- Gregg Turkington as Toby Determined
- Matt Chapman as Abuelita
- Dee Bradley Baker as Sprott
- Kari Wahlgren as Shandra Jimenez
- Additional voices:
- Casting by
- Soos now has folk songs written about him by the people he had helped throughout the episode.
- Wendy had always wanted to drive a tank, and had failed her driving exam.
- Dipper and Mabel's allergies go off at the same time.
- Ghost-Eyes majored in philosophy.
- The Corduroys train for the end times instead of celebrating Christmas.
- The episode continues immediately after "Dipper and Mabel vs. the Future," following Bill's success in opening a gateway to the Nightmare Realm.
- In "The Last Mabelcorn" Bill says, "I've been making deals, chatting with old friends, preparing for the big day." In this sentence he foreshadows his entrance with other demons into Gravity Falls' world.
- Bill also refers to Dipper as "His old puppet", making reference to the events of "Sock Opera."
- The snake and the badger from "The Love God" make an appearance running out of the forest.
- Chutzpar, the Manotaur from "Dipper vs. Manliness," is seen fleeing the forest with other animals.
- Tyler Cutebiker is shown as Gravity Falls' mayor after winning the election in "The Stanchurian Candidate."
- Rumble McSkirmish reappears when the Arcade is flooded with a weirdness wave.
- Gideon is shown to still have possession of a newspaper clipping of him and Mabel from "The Hand That Rocks the Mabel."
- Bill destroys all 3 journals except for a single page which is then blown away.
- The Pterodactyl from "Land Before Swine" can be seen on top of the Gravity Falls Mall.
- Bill Cipher's page from the opening theme is seen with a hole where Bill's picture should be, nodding to the fact that he has finally entered Gravity Falls' dimension.
- At the end of the opening theme, a faint whisper can be heard that is different from the ones heard throughout the show. When the theme is reversed, Bill can be heard saying "I'M WATCHING YOU NERDS."
- A remixed, apocalyptic version of the theme song is used for this episode where Bill and his minions replace the main characters in every shot.
- 618 appears on the truck driven by Ghost-Eyes and Gideon.
- The box that contains Ford's Quantum Destabeliser is labeled "Experiment 618."
- The weirdness bubbles that Dipper and Wendy go through turn them into birds, anime, food, and live-action versions of themselves. The weirdness bubbles Gideon and Ghost-Eyes go through turn them into polygonal, female, and rag versions of themselves.
- The cryptogram in the episode's credits reads, "KB HTMT IHOV 1,000 AMLCT WDY XZOM MLCG'H TSCGKFWFA IV VVEWYDUQIBXV CVO HIMC OI'J DINV, IM'H NSZPO EZ CM KLVP EZLYLG." Once decoded using the Vignère key CILLBIPHER, it reads "IT WILL TAKE 1,000 YEARS FOR TIME BABY'S MOLECULES TO RECONSTITUTE. AND WHEN HE'S BACK, HE'S GOING TO BE VERY CRANKY."
- The cryptogram in the episode's end page reads, "17-23-11-19 15-5 9-2-19-6, 23-10-20 15 1-9-10. 10-9-1 15-4'5 4-15-11-19 4-9 5-4-23-6-4 4-16-19 18-3-10. 15 23-12-1-23-25-5 12-9-2-19 21-9-6-6-3-8-4-15-10-17 12-15-2-19-5. 10-9-1 12-19-4'5 5-19-19 1-16-15-21-16 8-15-10-19-5 5-3-6-2-15-2-19-5." Once decoded using the combined cipher it reads, "GAME IS OVER, AND I WON. NOW IT'S TIME TO START THE FUN. I ALWAYS LOVE CORRUPTING LIVES. NOW LET'S SEE WHICH PINES SURVIVES."
- The title card flickers from "Gravity Falls" to "JUDYLWB IDOOV," which, when translated with the three letters back Caesar cipher, says, "GRAVITY FALLS."
- This also appears in the Water Tower in a short second where the screen turns static.
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