Just like every insane entity in all of reality and not-reality, Bill Cipher thought he was dead. They wiped Stanley's mind and everything with him in there. Which, to be fair, wasn't very nice of them. They tricked him, the one that knew everything. They tricked him so easily, and erased Stanley's mind. It could only go to say that Bill Cipher was dead, in every sense of the idea.
So, it surprised him a little to find himself not-so-dead. Bill tried to imagine every inconceivable way, and eventually, every conceivable way, that he could still exist. The triangle entity paced on a non-existent floor in the blank non-existent world of nothingness and flat-out had no idea how he could've survived. So, he did what any insane entity would.
"I am so lonely," Bill concluded blankly after a fit of laughter at his own joke. How long had it been? Days? Years? Eternity? Backwards? Sideways? Upside-down with a cherry on top? It surely felt like all of the above. Time has no meaning and meaning is dead. At least here it is. Where-ever 'here' is. Cipher had done everything and nothing he could. Either being dead is not all it's killed up to be, or being alive while being dead is not all it's lived up to be.
"Dipper! Dipper come on!" Bill heard distinctly distantly. 'Shooting Star' Mabel Pines. She sounded different.
"Just- Gimme a Sec! Where the hell is my hat?" Pine Tree muttered. Something was very strange about this. Bill liked that idea. Suddenly, slowly, everything had faded back into reality. Bill Cipher could see was going on and now, he realized, he was alive again. Or maybe not. It was getting hard to tell. Bill found himself perched mid-air in the middle of the Mystery Shack. Which was very unusual, to say the least.
He noticed Stanford and Stanley Pines. The two did not seem especially different, outside of the fact that they were actually laughing and smiling. Bill raised a non-existent brow to this. Maybe they hadn't actually erased Stanley's mind fully after all. That might explain his existence. It was always the simple things Bill tended to miss. He should've been able to realize those two had swapped places. That was so simple. Such a simple trick had almost killed him, erased him from existence. Bill decided that he would have to focus on the simple, normal, easy things more. No more being tricked so easily, no more missing the simple answers.
'Pine Tree' Dipper Pines descended the stairs with a light skip. He now a tall, gangly teenager, somewhere around 16. Focusing on the simple things... It was already boring him. The triangle entity floated down to eye level with the rest of the Pines and watched Pine Tree smile.
"Okay, found it." he said shifting the cap slightly on his head, "….Uh. Mabel? Where'd she go?"
"I'm right here, goof! Come on! We'll be late! Soos is waiting for us!" Mable announced herself with a gigantic, brace-less grin, leaning out the door of the shack.
"Fine!" he said, jogging to the door with a light wave to his Grunkles, "See ya later!"
"Have fun kiddos!" Stanley smiled.
The door swung excitedly shut, and the old twins started talking about things Bill began to ignore quickly. There were things to test. The first of which Bill tested was actually moving freely out of the room. He remembered the whole fiasco with the unicorn hair and wanted to make sure that he wasn't trapped in this dumb shack. Of course, the unicorn hair spell had been broken when they re-built. So Bill Cipher found himself able to come and go as he pleased. Bill smiled an non-existent smile. Officially outside of the shack, he plucked a cane from nowhere and put it back after a slight dance. Pausing time and messing with some local wildlife, Bill eventually brought himself to various places throughout the town briefly inspecting the town.
His last test was the one he was a little hesitant to try. He brought himself to the edge of the town's limits and squinted at the imaginary wall. He tapped on it's invisible wall, and sighed. Trapped. He was still trapped. Of course he was. He floated upside-down and walked up the sky. Why had he been brought back to the reality of the living if he was being forced to be trapped here. At least it was the weirdest town he knew.
The creature was watching him from below. Bill Cipher flipped himself back around as he noticed it, floating down in front of it. It couldn't actually see him, could it? The magical animal was staring at him, he was certain of it now, its eyes had followed him from the sky to in front of it and was definitely looking at him. It tilted its strange-looking head and Bill raised half a non-existent brow at it.
"Boo," he said as it looked at him. He huffed a laugh, "What are you looking at?"
The creature tilted it's head forward slightly and it's white iris flashed slightly. Bill Cipher fell to the ground with a thud before he could wonder what it was doing.
"Ow," he said, his voice slightly different, more, normal. This was strange. Bill Cipher looked closely at his five-fingered hands and prodded his arm. Patting down the face that was fully his own, he frowned. He was in a human form. Bill glared at the creature. How the hell did it do that? How could it have seen him? He was a Dream Demon. Magical creatures were no exception to his powers and the rules of his reality.
The creature smiled. Its smile was exceptionally creepy. The thing started to scare him a little. However, he was more angry at it.
Almost without thinking he growled, "Okay, this isn't funny," attempting to threaten it with his power, mostly ready to kill it. Which fizzled out with a light blue puff.
"What?" Bill screamed in anger. His two eyes flashed in red. The creature was gone. He picked himself from the grassy ground and searched the area. He tried to conger something, anything. Sighing in relief when a light blue flame surrounded his new hand, Bill frowned again. That creature must have stopped his power. How could it do all of that? He shook off the blue flame and began to hover slightly off the ground, and wondered.
Bill Cipher was walking, unsteadily, along the facade of the Mall. He had walked all the way from the forest and was actually very unsure of where he was planing to go and why. There, Mabel Pines jumped in front of him.
"Hi!" she exclaimed with a bright smile. Dipper caught up to his sister and patted her shoulder before looking at Bill.
"Uh..." he started as he stared at the Pines twins.
"Quick! Act like a normal human!" his triangle-self said as he popped into existence.
"Why? That's no fun!" another one of himself said as he appeared.
"We want to get back to our regular form don't we? Those two are a one-way ticket to all the answers!" another said.
"We could kill them now and figure out how to get back to normal afterward. Two annoying birds and a ton of stones!" one laughed manically. The human form of Bill smirked a little at this.
"We could use them and have fun while we're at it!" another said as he appeared, "Besides, how fun is it just to kill them now?"
"You have a point. I agree with whichever one of us just said that." one laughed.
"Let's act like a sorta normal human and use them and all the while we can have a little fun!" they all concluded at once. All but one dissipated and the imaginary triangle version of himself frowned an invisible imaginary frown.
"Uh- how do normal humans act?" he asked himself before the last triangle version of himself disappeared.
"...Hi?" the human Bill said with a confused smile.
The twins looked at each other. Mabel was beaming as Dipper gave her a frown. They looked back at Bill Cipher, in the most unsuspecting form, and Dipper shot him a look of suspicion.
"My name's Mabel! And this is my dorky bother Dipper! I've never seen you in town before, but, then again, we just visit in the summer so you could've lived here the whole time and we've just never crossed paths." she said beaming.
"Anyway" she sung, " It's nice to meet you! What's your name?"
"Uh..." Bill Cipher seemed to find himself stuck.
Mabel continued to smile and nodded a little and moved her hands as if to push him into telling her a name.
"Bill," he said quickly, before swiftly adding "-ie! Billy!"
"Nice to meet you, 'Billy'." Dipper's look of suspicion deepened and his sister elbowed him, he loosened in response, "I'm sorry. My sister is insane." Dipper concluded.
The corner of Bill's lips twitched up and he continued to give them a bewildered stare.
"Snap out of it Me!" a triangle version of himself screamed, "You are a Dream Demon! Come on!"
"Uh." he continued.
Mabel frowned, "See, you've broken him Dipper."
"What?" Dipper Pines protested, "Really? I broke him?"
"Huh?" Bill muttered.
"Yeah! He probably can't handle your nerdy-ness!" Mabel smiled.
Dipper laughed, "I didn't even say anything nerdy! It was all you."
"Guys!" Grenda said happily as she slapped their shoulders heavily.
Bill jumped, "Guah!"
"What's wrong with him?" Grenda said pointing at the human dream demon.
"There's nothing wrong with me! I'm completely normal!" Bill said quickly.
"What is wrong with us? You're acting completely out of character." his triangle-self told himself as he appeared again, "What would the writers say!?"
Mabel laughed, "There's no such thing as 'normal'! Everyone is a tad strange."
"Except Tad Strange," Dipper added with a grin.
Grenda laughed hardily at this and then looked confusedly at him.
"Inside joke." Dipper smiled.
"Sorta." Mabel shrugged. Candy walked up to them, with her hands full of slerpies of various colors.
"Oh, hi, who are you?" Candy said as she distributed the drinks among the teenagers.
"This is Billy!" Mabel said with a gigantic grin, "All he's said so far is 'uh' and his name."
"Uh..." Bill began again. He bit his lip, forcefully, hoping to force himself to say something more.
"A pleasure to meet you, Billy, I'm known as Candy," she said with a smile and an outstretched hand after handing the final drink to Grenda.
"Uh...Yeah." He finally managed, taking her hand shacking it quickly and snatching it back as he noticed the temperature, "Cold!" he said aloud, shacking his hand a little.
"Oh, sorry." Candy said as she rubbed her hands together.
"You can speak!" Mabel said in false disbelief. She started in a fit of giggles.
Bill raised a brow at her. Humans were weird creatures. Dipper rolled his eyes at them all and put on a false smile.
"Of course I can speak..." Bill murmured.
"Ha, at least this body has a mouth." a triangle Bill laughed.
Mabel and her friends giggled again and she socked him in the shoulder, "This guy!"
He looked at the place on his shoulder that she had hit with curiosity, glancing back at Mabel who was currently beaming at her friends and Dipper. Dipper rolled his eyes at Mabel and wrapped his arm around hers, linking their arms together.
"We better get going, see you around maybe?" Dipper said, still glaring at him.
"...Yeah." Bill muttered, quietly hoping that they wouldn't see this version of him again.
"Ooh! Wait, Billy, why don't you come to the Northwest's party tomorrow?"
"Mabel." Dipper quietly complained.
"Uh... I don't-"
"It'll be great! Come on! I insist!" She said quickly glaring at her friends and elbowing Dipper.
"Yeah! Party!" Grenda said enthusiastically, punching the sky.
"It would be quite interesting with you there." Candy said with a light smile.
Dipper continued to glare as Bill Cipher's eyes stayed stuck curiously on Mabel. Shooting Star was really trying hard to befriend him. It was confusing. Mabel elbowed Dipper again.
Finally, he resigned himself to groaning out, "Yeah, I'm sure everyone would love to meet you."
"I still don't-"
"Please!" Mabel said clasping her hands together, pleading.
Bill finally got curious enough about the whole thing to resign and agree to go. The group left with waves and good byes after Mable gave him the details. Bill looked around the area and once again wondered what he was even doing.
"Well, I guess that went well enough," Bill muttered sarcastically as he kicked at a few pebbles on the pavement.
"What even WAS that!?" Bill Cipher roared, directing a three-fingered hand at his main human self.
"I have no clue Bill, but I think our boy has gone bonkers crazy in the wrong way." another said into a pretend microphone.
"Well, he better clean up his act or he's going to be dead meat at this party he's agreed to be at." the first Bill commentated.
"True, true." the second agreed into the microphone, "However, this might actually be a good thing."
"How so?"
"Acting so out of character may have actually saved him from Pine Tree, Shooting Star, and Co. from finding him out and murdering him in this weaker body. Who knows how easily he can get killed out here."
"Ah, I see. It is a little strange, considering he wasn't doing this on purpose. I'm a little concerned for his insanity."
"Oh shut your eye Bill." His human-self growled, forcing the triangle commentators to disappear. He paused in his aimless walk and straightened, wide-eyed. His self had a point. He brought himself to the edge of town, just close enough to the Mystery Shack that he could see it. He strolled curiously toward it, taking his time to inspect the place.
"Hey dude! Wanna visit the most Mysterious place in Gravity Falls?" Question Mark, or Large Hairless Gopher if you prefer, invited, with a dumb smile on his face. Bill Cipher hid a grimace and sighed.
"Actually, I'm a... friend of 'Dipper' and 'Mabel'," Bill told him, pretending a smile.
"Oh, well those dudes are out with some of their buddies, they'll be back tonight though, want me to tell them you stopped by?" Soos smiled, adjusting the fez on his head.
"Oh, they invited me to a party at the Northwest's. I was wondering where that was..." Bill lied.
Soos thought hard for a long moment before smiling, "Yeah, I can help you dude, I'm still all confused when I look for their house too. Without that big hotel-lookin' house, I can't tell which place is theirs." Soos said as he led Bill in, briefly looking back at him as if for confirmation.
Bill quietly glared at the Shack's gift shop and upon noticing Soos's glance, briefly gave him a pained smile.
Soos grabbed a small map of Gravity Falls saying, "Okay, dude, here you go, it's around here." he pointed at a small spot on the edge of town, fairly close to the Dinner.
"Okay, thanks..." Bill said, handing it back to him and looking around a little more.
"What are you even doing here?" His triangleself asked.
He shrugged to himself.
"No problem dude. Oh, and what you did to your hair's awesome dude."
"Hum?" Bill looked up and ran a hand through the hair he had hardly even paid any attention to.
"Yeah, it's awesome."
"Thanks?" He murmured, pulling a bright yellow-blonde hair into his eyes. That seemed fitting. All too logical, it was actually a little annoying. He wondered what he actually looked like as a human for a moment.
"Hello, Soos," Stanford said, his eyes focused on his journal. This one was new and a tan leather unlike the original three, causing Bill to stare at it.
"Hey there Mr. Pines!" Soos said with a smile.
Stanford glanced up and stopped on Bill. He raised a brow at him and frowned.
"Hello, young man..."
"Hi." Bill Cipher grinned, "What's the book for?"
"Oh, it's just a journal," Stanford said tapping the eraser of the pencil on the open page.
"What kinda things do you write in it?" Bill pressed.
Stanford glared at him a little, "A little bit of scientific analysis, mostly a collection of random thoughts nowadays though."
"Huh." Bill shrugged, "Thanks again -Mr..." he grinned to Soos.
"Soos. Dude, it's no problem."
"Soos, okay. Yeah, thanks." He nodded, walking out of the Shack.
"Who was that?" Stanford leaned to Soos, closing the journal as he glared, suspicious.
"Him? A friend of Dipper 'n Mabel."
"Really?" he glared, "What did he want?"
"Just to know where the Northwests lived now."
"Why?"
"The guys invited him to the party... What? Is he actually some kinda monster? That could explain his awesome hair."
Stanford gritted his teeth and pulled the journal closer as he opened it, "It's probably nothing. He's just- a little, familiar."