Ford and the rest of the Pines are sleeping in the Mystery Shack, and he has a confrontation with Bill in his dream. Bill greets Ford, and reveals that Ford cannot keep the rift safe forever. Ford angrily says that Bill has no control in his world. Bill states while he does not have control now, "things change." Ford wakes up in panic from the dream, then he has a family meeting the following day announcing that Bill is planning to invade the real world. In order to protect the Pines family, they need to Bill-proof the shack. They have everything except one ingredient: Unicorn hair. And the most pure of heart has to go. Mabel offers to go with Wendy and her friends. When they arrive at the Unicorn's hollow, the Unicorn says she is not pure of heart. Mabel then spends the rest of the day doing good deeds to prove herself pure of heart.
Meanwhile, Stanford shows Dipper a secret study he has. This study has a machine that can read thoughts and protect his mind from Bill. Dipper asks Ford about Bill, then Ford tells Dipper that Bill intends to retrieve the rift that was created by the portal, which Bill will then use for his nefarious purposes. Ford also dodges the question about what happened between him and Bill years ago. Ford hooks Dipper up to the machine and Dipper's thoughts are beginning to be scanned when he decides to try the machine out on Ford to see what happened with Bill in Ford's past. He sees Ford's thoughts, revealing a deal between Ford and Bill years ago. Then suddenly Ford wakes up and traps him by the wall. Dipper thinks that Bill is possessing Ford, and he threatens to wipe out Ford's memory. In retaliation to these claims, Ford takes off his glasses and proves to Dipper he isn't Bill. Ford reminds Dipper that he has a metal plate inside his head to prevent Bill from possessing him.
On the other half of the story, Grenda, Candy, and Wendy are planning to sneak in while the unicorn is sleeping and cut off some hair. The satyr blows SOS on the pan pipes, before Grenda puts it to sleep with a cloth soaked in chloroform. They are just about to cut off the hair when Mabel stops them, holding the scissors. The unicorn wakes up, sees Mabel holding the scissors and gets even angrier, saying she isn't pure of heart. Suddenly two more unicorns appear from the bushes and announce that this is all a big scam for the unicorns to make people leave them alone. Mabel gets mad at this and a fight breaks out.
Ford reveals his past with Bill. They both apparently used to be great friends. Ford learned about Bill in some weird incantations in a cave he discovered. He recited the incantations out loud, but nothing happened until later that day during his dreams when Bill met him. They played a game of interdimensional chess, and from then on Ford became good friends with Bill. He let Bill enter his mind whenever he wanted and worked with him to develop the idea of the portal, until Fiddleford had a glimpse inside the portal and saw Bill's true plans. From then on Ford knew that Bill had betrayed him, and went against Bill and shut down the portal.
In the end, Mabel did get the unicorn hair, and the shack was Bill-proofed. Bill watches over the Shack from his own dimension,stating that while he can't possess anyone inside the Mystery Shack, he has all the other people in Gravity Falls to do his bidding.
- Written by:
- Directed by:
- With the Voice Talents of
- Additional voices
- Casting by:
- Ford's middle name is Filbrick, after his father.
- Bill and Ford used to have a friendship.
- Ford has a metal plate inside his head.
- Mabel's first word was "unicorn."
- Stan can speak Spanish.
- Mabel has been banned from a petting zoo for taping a traffic cone to a horse's head.
- Wendy stopped believing in unicorns when she was five years old.
- Ford's Electron Carpet first seen in "Carpet Diem" returns.
- The interdimensional rift revealed to be created by the portal in "Dungeons, Dungeons, and More Dungeons" appears.
- Stan is seen pug trafficking, first mentioned in "The Stanchurian Candidate".
- Dipper and Mabel recall their defeat of Bill in "Dreamscaperers" and "Sock Opera".
- The door to Ford's private study from "Not What He Seems" appears.
- Scenes from "Tourist Trapped", "Into the Bunker", and "Not What He Seems" appear in Dipper's thoughts.
- Dipper still loves the song Disco Girl from "Dipper vs. Manliness".
- One of Dipper's projected thoughts read, "I miss Tyrone", who was the first Dipper clone from "Double Dipper."
- Ford's initial trust of Bill could briefly be seen in one section of the Journal 3 entry seen in "Dreamescaperers," in which Ford fondly regards Bill as a friend before being scratched out and replaced by a warning not to trust him.
- 618 appears on Stanford's chalkboard, as well as it upside-down (written as 918)
- Dipper still has a crush on Wendy, despite the events in Into the Bunker
- Soos does not appear in this episode.
- The title is an allusion to the 1968 Peter S. Beagle novel and 1982 animated feature film "The Last Unicorn."
- In addition to this the cryptogram at the end of the episode is translated using the Vigenère key SCHMENDRICK. Schmendrick is the name of a main character in "The Last Unicorn."
- When Dipper is hooked up to Project Mentum, there are several screens with this thoughts displayed, with each line repeating as it scrolls to the right:
- 1st Screen:
- Oh man, I can't believe I'm with the author!
- Gosh, I hope no one was looking!
- Maybe if I cross my legs, no one will notice!
- Kinda kinda hungry, but could also not eat.
- I should really try out the president's key sometime.
- I could probably I could probably rob a bank.
- I miss Tyrone!
- Phrases scrolling across 1st screen:
- Is my fly down?
- Disco Girl
- Coming through
- 2nd Screen:
- Ugh, this is so hard! I've been here forever!
- Eeeny meeny miney you.
- Is Bill indestructible?
- What's his secret?
- Who stole the capers?
- Why does he have to be so mysterious about Bill?
- I can handle the truth!
- 3rd Screen (same phrase for all 7 lines):
- I wonder what Great Uncle Ford is thinking
- 4th Screen (same phrase for all 7 lines):
- Use the machine, it'll show you his thoughts!
- 5th Screen (same phrase for all 7 lines):
- Just a peek!
- 6th Screen (same phrase for all 7 lines):
- He wants your help he just doesn't know it
- 7th Screen (the two phrases alternate lines):
- Yes, you are!
- Astute, I would say, good observation Dipper!
- 1st Screen:
- When Dipper puts the helmet on Stanford, his thoughts are projected in six lines, but they are not scrolling in the same pattern as with Dipper. They pull apart to reveal an image of Bill. The lines are:
- I can't tell him, he's not ready.
- The grand unified theory of weirdness.
- I miss dimension 52.
- I'm sorry Fiddleford
- The people Bill shows are, in order:
- Candy; Pacifica; Tyler Cutebiker; Lazy Susan; Manly Dan; Robbie; The two men from the time paradox avoidance enforcement squad; Sheriff Blubs; Deputy Durland; Toby Determined; Preston Northwest; A member of the Society of the Blind Eye; Blendin Blandin; Shandra Jimenez; Soos; A toddler; Tambry; Bud Gleeful; Grenda; Lee; Priscilla Northwest; Mr. and Mrs. Valentino; Wendy; Old Man McGucket. [Once it reaches Old Man McGucket, the list repeats itself.]
- The cryptogram in the episode's end page is 15-10 21-15-8-16-19-6'5 17-23-11-19 16-19 10-19-19-20-5 23 8-23-1-10, 22-19 5-3-6-19 4-9 13-10-9-1 1-16-15-21-16 5-15-20-19 25-9-3'6-19 9-10 which, when decoded using the Combined Cipher, reads: IN CIPHER'S GAME HE NEEDS A PAWN, BE SURE TO KNOW WHICH SIDE YOU'RE ON.
- The cryptogram in the end credits is S UPYTYH DIP GAVO QETHI MCBK OHK XEXJB VRW YOUWCHIA VRSV OQ LRDIA, which, when decoded with the Vigenère key SCHMENDRICK, translates to A SIMPLE MAN WITH EAGER EARS MAY TRUST THE WHISPERS THAT HE HEARS. The key is found on a stump when Candy, Grenda, and Wendy enter the Gnome's tavern.
- The Code in The Cipher Folder under 'Mind Scape' is reads 'Black and & White'
- Codes on Stanford's chalkboard (separated by semicolon means they were written above each other):
- on; ap; es
- __te; py
- 6 1 345 12 89 10 11 1
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