(This takes place somewhere Not What He Seems and The Last Mabelcorn.)

(Bill POV)

"BILL YOU STUPID TRIANGLE GET BACK HERE!"

Bill, more accurately Bipper, was running from Shooting Star. He had gotten stuck in Pine Tree's body and was still trying to find away to get out. Of course, Pine Tree had been insufferable. Bill couldn't go a minute without having to listen to him list all the reasons why Bill should never have possessed him in the first place.

Bill ran into a wall and fell to the ground. 

"HA! Pain! Never gets old!" He mumbled weakly.

Shooting Star somehow managed to catch up to Bill. She grabbed his wrist and pulled him up.

"Alright Bill, enough with this whole puppet thing, I know you're in Dipper's body so GET. OUT."

Bill panicked, "I-I can't!"

Shooting Star slapped him, "What do you mean Bill?!"

Bill backed away and sat down, "I forcefully possessed Pine Tree cause I thought it would be fun and now I'm stuck in this sweaty preteen body.... likely forever. AND I WANT TO GET OUT. Please don't kill me."

That got her attention. Shooting Star ran away.

"Hey! Shooting Star! Where are you going?"

He followed her into her and Pine Tree's room. She was rummaging through her pile of randomness and finally managed to find something.

"Wha-what's that Shooting Star?" He said nervously, hoping it wasn't a weapon.

"A sock," She held it up and shouted, "Dipper! If you can hear me use the sock to talk to us!"

Bill shushed her, "Fez and Sixer are still here. I don't want them finding out about this."

Suddenly the sock twitched and spoke, "Mabel!"

"Dipper! Bill's stuck in your body and I don't know how to get him out!"

"Ugh, I know that. We have to tell someone!"

Bill hit the sock, "No! No one can now about this! It's too risky, they could kill me! Or try something crazy and destroy Gravity Falls! And potentially the world."

Shooting Star scowled, "We have to at least tell someone!"

Pine Tree spoke again, "Someone smart enough to help and trustworthy enough so that no one else will find out..."

Bill chimed in, "And not Sixer please, that would be disastrous."

(Mabel POV)

"McGucket," she suggested.

"Glasses? Really?" Bipper said unamused.

"What? He's very smart, and after the encounter with the memory guys he's getting more normal," she argued.

Sock Dipper shook his... head? Sock...face...?

"Nope, I think we should tell great uncle Ford, he'll know what to do!"

Bipper frowned, "No! I don't want Sixer to have anything to do with this."

"What? Why? Ford's a great guy!" Dipper said.

Bipper clenched his fists, "Arrhgghhh! I vote we tell Glasses. Anyone's better than Sixer."

(Dipper POV)

Ugh. Dipper was extremely mad with Bill. Forcefully possessing him? Refusing to get out??? Dipper wondered if Bill was actually stuck or just faking it for fun.

He floated besides his sister and followed her and Bill downstairs into the kitchen where they saw...

"Six- uh Stanford!" Bill blurted out, "Uh, wh-what are you doing here?"

Ford took a sip of his coffee and looked him directly in eye, "I live here."

Mabel squeezed Bill's shoulder, "Dipper and I were heading out to see Old Man McGucket."

"Fiddleford? Really? Can I come with you!" Ford grinned widely, "I-I really need to apologize."

"NO," Bill said, "You have to stay away!"

Ford looked suspiciously at Dipper, "You okay kid? Seems like you've had a bit too much Mabel juice."

Bill waved his hands wildly, "NO NO NO, COME ON SHO-MARBLES! LETS GO!"

"It's Mabel actually," she said about to walk out, but Ford stopped her.

As Bill tried to run away, he grabbed him and Mabel and stared at them, "Okay kids, I can tell something's....off. So tell me, what's going on?"

(Mabel POV)

Mabel sighed. Grunkle Ford was very powerful and very smart and he could probably help...

"Okay Grunkle Ford, that's not actually Dipper that's Bill, uh Bipper. He forcefully possessed Dipper and now he's stuck."

Ford's mouth opened, then closed, "...fascinating."

(Dipper POV)

Dipper decided now would be a decent time to speak, "Uh, I'm a sock now."

Ford let out a small scream, "DIPPER! Wha- I mean, Bill getting stuck is believable but you can't just be a floating sock! WAIT... THATS MY FLOATING SOCK."

Dipper moved towards him covering his mouth with the sock, "No no, I'm like a ghost, the sock is just a thing for me to speak out of."

"Huh, a way to communicate, of course! Yes that makes sense" Ford exclaimed, then he went quiet, "Um, bad news though. Bill may be stuck permanently."

Bill sighed, "Yep I knew it."

Ford patted Dipper's sock, "Alright guys, I'm tired so you all go away and let me figure this out later."

Mabel frowned, "But Grunkle Ford it's like 10:00 AM."

"I'm old!" He said walking out of the room, "I can feel tired whenever I like."

There was a moment of silence. Then Bill spoke up, "Hey Dipper, are you  aware that you're going to turn into dream demon soon?"

"WHAT!?"

"Yeah, just a triangle."

Mabel's eyes lit up, "Oh I know that!"

"How do you know that?!"

"I read a fanfiction."

"Ah."