Holy Shit I do not want to mess this one up. Just recently got into the fandom, it will probably follow some of my other stories. Please review my work I do not make any claims to this. Not a lot of supernatural elements to this, no Triangle or end of the world. I do not own Gravity Falls or The Rocky Horror Picture Show which will only play a small roll in the overall story(Saw it this weekend and thought this could work).

Dipper pulled his vest closer to his body. It was freezing cold in Washington and he wondered again why it was his sister chose to go there of all places for college.
Then again she enjoyed being random like that. Not to mention according to her it was the easiest way to get Canadian weed and other illegal items like fireworks. She had somehow gotten into a lot of bizarre things like that. He for the most part let her do her own thing. He had graduated from his private school early, a few years to be exact. This gave him a lot of time to travel the country.

So when he got an invitation from his sister to attend a show that she was in at college he decided to go. It was better than hanging around his parents house. Not to mention it had been a long time since he saw her, he was usually traveling while she was at home and vice verse.

Dipper came to the large building where it was supposed to be held. He checked his phone again just to make sure before he entered. Yep right number. It was cold for halloween weekend. He entered the building and made his way through a few dozen hallways that seemed to be continuously falling back on itself. He finally heard some talking, excited voices, a lot of scuffling and scrapping of bare feet. Dipper took a deep breath, he had just come in from being on the road actually.

About two weeks, he had stopped briefly at a typical mail box where he could receive letters, and lo and behold from California one that had come from Washington State, smelling of glitter, illegally imported smile dip and close to three pounds of stickers was a letter from his sister. The calligraphy left something to be desired but he puzzled it out.

The next few days he spent on a plane and then walking into town, it made him feel more dramatic. Now though he was sweaty, a little smelly and ready for a show that his sister had promised.

Dipper had never seen the show before so when he stepped around the corner that lead to what appeared to be the entrance of a movie theater he felt as if he had descended to a new planet. Men in drag, women in fish nets and everyone in various other costumes. He didn't know where to look or if he was even allowed to look. A couple of guys made kissing faces at him and he was positive that he saw a girl dressed in a suit being covered in fake blood.

The temperature raised by ninety degrees and he pulled at his vest taking it off.
"May I take your coat sir?" Dipper felt a tap at his back, he turned around to tell the person no that he was fine when he was struck speechless.

Standing before him was Pacifica Northwest, a girl he knew for a few years when he vacationed with his sister and uncle. She had been rather rude at first but time made her nicer. She eventually turned into a close friend with him and his sister. He had heard that the two of them had gone to the same college. Strange as it was a public one and she had enough cash to rent out all of grand central station for a week.

She was a black lacy bra a cup size or two too small. It was only a F cup so she was almost pushed out of it, he could make out a bright flesh colored nipple underneath it. She had on a black leather thong that rode up between her butt cheeks and they were free to the air. The finishing touches was a pair of bright white bunny ears that sat at the top of her head.

"Pacifica!" Dipper said surprised. She stood aghast in front of him, recognition slowly dawning on her face.

"OH SHIT! DIPPER!" She shouted, she covered her blushing cheeks before moving in front of her toned exposed body. "What are you doing here!"

Before he could answer the pattering of feet and then an attack hug from behind caused him to gasp. Tiny doll hands covered his eyes and a pair of breasts covered his ears. He could just hear a muffled.

"GEUSS WHO?!" That was probably from the noise level from how thick and creamy the tits were.
"Hey Mabel." Dipper said nonchalantly. She still gasped surprised.
"How'd you know?" He turned to respond and felt his jaw drop a little. If Pacifica was wearing little his sister was wearing even less. An impromptu duct tape bra and panties made out of dark electrical tape. A swimsuit would have covered more.

"Oh JEEZ!" Dipper cried covering his eyes with one hand. Giggling from Mabel told him that she was at least enjoying his suffering. An agitated huff from Pacifica told him she at least was as annoyed as he was.

"Why didn't you tell me he was coming?"
"Ha! Cum." Mabel said quietly. Pacifica snorted and began laughing too. Dipper slowly removed his hand and kept his eyes locked on the two girls foreheads. Mentally slapping himself that he would even think of gazing at their breasts.
'Their full, perky, young, smooth glorious tits...STOP THAT!' he mentally slapped himself.

"What's so funny?" Dipper managed to squeak out.

"Ah little brother so innocent, so young." Mabel tutted. "You've never seen the show right? You are gonna love it, guarantee."
"What are you two supposed to be anyway?"

"We're ushers! Clearly!" Mabel stated it as if it was an obvious fact. Dipper looked at them again and all he could see was a couple of playboy bunnies. They both certainly had the figures for it. Pacifica was fit and trim, her hips jutting away from his waistline, her breasts were the fullest feature of her beside her breasts. Her wavy blonde hair continued that illusion. Mabel was a little chunkier, her diet of indulgence and very little exercise was balanced by her enjoyment of just plain moving and also good genetics. Her stomach seemed to move slowly and softly to her waist and thighs, her boobs were a little smaller than Pacifica, quite an impressive handful.

"Clearly." He responded rolling his eyes. He flushed dark purple and he felt his nose get a little stuffy, almost like a nosebleed. "Isn't this a little lowbrow for you?" He said to Pacifica who also turned beet red and ran her fingers through her hair.

"Well I learned Mab's was doing it and I wondered why my roommate was coming in late steaming in sweat and looking super content. Turns out it is great for endorphins."
"Wait the two of you are roommates?" Dipper said surprised. The two exchanged knowing looks that he could not puzzle out.

"Well we go to the same college, makes sense right?"
"I guess so. What is the play about anyway?"
"Oh you'll see." Mabel said mischievously. Dipper rolled his eyes at her aloofness, he could handle it. "Whatever. I need to find a seat."

"Oh! Can we strip you first?" Mabel said excitedly. Dipper's eyes widened and his heart dropped to his knees. "It's part of the show you see!"

"Not to mention that sweat lodge gets to be like a million degrees in there. You'll thank us later." Pacifica said with a smirk at his discomfort. Dipper moaned and pulled off his tshirt and vest pushing them into Pacifica's hands. She flushed at the suddenness of it all. That and his impressive body structure, he had a tight hard stomach and his arms were also impressively cut from long hard treks. Also unexpectedly were some cuts and bruises. Mabel gasped at them and caressed some of the older smaller scars.

"What happened brobro?" Dipper flinched a little away from her prying hands.
"It's nothing, a few incidents on the road, nothing else." Mabel glowered at his complete brush off. He then bent and pulled down his pants. His boxers were blue and red. He was completely red now. As was Mabel and Pacifica.

"I'm keeping my hat on. I'm not a savage."
"WOO! Dipper! Going full out!" Mabel said excitedly grabbing his pants and running off with them.
"My Wallet had better still be in there!" He called after his sister's excited retreating form. Pacifica burst out chuckling at the look on his face. She smiled at him and stuck out a hip to lean on.
"What?"

"You didn't need to take it all off, it's not like a rule or anything, you could have totally gone with just the shirt." Dipper growled in annoyance.

"It would be pointless to go after her now right?"
"Yep. But in compensation." She grasped his arm tightly and pulled it to herself. "I can have the prettiest girl in school escort you to your seat."
"Cool where is she?" Dipper said trying to sound nonchalant, he was inwardly freaking out, he felt his heartbeat go through the roof and he felt something stirring in his loins. He had pleasured himself once a few weeks ago in a forest, but that was just to keep his mind clear and it had been the middle of the night so no on had seen it.

He allowed himself to be half dragged to a seat that she chose. There were multiple aisles around the room and seats that faced an enormous tv screen.
"What's with the excess space?"
"So the ushers can dance in between duh."

Dipper flushed again at the concept.
"Don't worry this is Mabel's and my section, we will take good care of you." Pacifica said before kissing him brightly on the cheek, he felt a smear of lipstick and some eye shadow left from her eyes, she was still wearing a pound and a half of makeup tonight. Dipper sat semiselfconsciously. He really wanted to be anywhere but there. Anywhere but with his sister and her roommate who he had just that moment realized were probably the most attractive women he had seen in a long time.

Suddenly a tap on his shoulder brought his attention to his right. Mabel was sitting next to him, her legs crossed assuredly and seductively. Dipper had to cross his own to hide the excitement that was slowly growing in his pants.
"Excited?"
"You could say that." Dipper responded. Mabel frowned and looked him hard in the eyes he twisted uncomfortably.
"What?"
"Were's your luggage? I thought you were coming from New Mexico or something?"
"I stashed in under a bush, we can get it after the show. I'll wander around until you guys wake up." Mabel balked at his nonchalant attitude.
"Dipper Pines! Are you telling me that you are just going to walk around for a few hours after this show instead of sleeping!"

"Yeah...I have no place to stay."
"Just crash at out place. Paccy won't mind."
"Paccy?"
"Her nickname Dipdop." Mabel's eyes lit up all of a sudden. She reached into her makeshift bra and took out a little red pill. She dropped it in his open hand and smiled.
"Take this halfway through the show okay?"
"What is it?" He said suspiciously.
"Just trust me this once okay?"

Dipper sighed but he kept it nearby. It would probably be some sort of illegal chemical, but he was going to trust her this once. The sequence of events happened rather quickly afterwards. IT was all a whirlwind of bareness, skin, tits, nipples, butts. Dipper tried not to look too freaked out and he was doing decently well for himself.

The lights began to dim and that was when six blondes with red lipstick stood in front of the assembly. Pacifica was among them with her off kilter lipstick. They began to sing and shout along with the movie. Moving their hips demurely; Dipper could only look on in amazement. It seemed so large, so grand and so...so...not Mabel and Pacifica's thing. Well Mabel maybe but Paccy? It was probably some kind of rebellious streak in her.

The show went very quickly and before Dipper knew it they were at where he would guess the halfway point was. He took the pill, popping it and dry swallowing. The girls were right, it was getting very hot in there. He had beads of sweat rolling down his body and he had to wipe away the sweat every few seconds. He took his hat off and fanned himself.

Suddenly a scream from his side caught his attention

"It's just a jump to the left." The old neckless man on the screen said. The people around Dipper did so before shouting at the screen "And then a step to the right!"

"Put your hands on your hips."
"Or someone else's TITS!" Mabel shouted in front of Dipper grasping a hold of her own and wagging the uncovered mameries in his face. She had at some point lost the bra and was now cavorting around basically naked. He was slowly getting turned on by his sister's body and he didn't know how to feel about that.
The line was repeated and this time it was Pacifica's tits that Mabel grabbed, Pacifica reciprocated the action, the two girls keeping eye contact with Dipper the entire time. He felt the stirring in-between his legs get even more intense.

That was when the ecstasy that Mabel had slipped him finally took affect. The rest of the show was a mixture of the colors on the screens intensifying and breasts being shoved into his face. Someone was sitting on his lap and grinding hard into his crotch at some point, her long hair getting caught between the two of them, another moment he thought that he was exposed completely and something was sucking hard and fast at his head, the very tip just engulfed in a thick warm tongue. The very next moment he was aware of some red pills floating in Pacifica's water bottle and that she and Mabel were sharing it.

That was when he realized that the two of them were tripping just as hard as he was.

At the end they were out the door and falling down the pavement, he could not even remember the entire show. He was holding up both Pacifica and Mabel, they were in matching tight black leggings, their rears and cunts showing through the fabric that was hugging their legs. Neither were wearing underwear. Dipper had gotten his clothing back but both girls were wearing his shirt and vest, they had lost their own shirts during the confusion. They stumbled upon Dipper's stuff instead of actually finding it for themselves.

He really only came back to reality when the three of them were sitting in the girls shared dorm room, the two beds pushed up together to form one large one. They had their shirts off and were exchanging sloppy wet kisses. Dipper was fascinated with running his fingertips across their burning hot bodies. It was as if he had been hit by lightning and all of his nerves were raw and supercharged. He alternated between Pacifica's breasts and Mabel's lips.

One thing that he did remember from the show was that free love was cool, that even sibling relations was cool. He smiled and moved down Mabel's neck and jawbone until finding her nipple, he took it in his mouth and began to slurp at it hard. He felt her shudder and moan, he looked up into her lidded eyes. He felt nimble fingers pulling at his own pants and over his back. Pacifica was working at the muscles on his back. Moving over the scratches and sweat stains.

Dipper gasped and pulled away from Mabel, he laid back in the bed and pulled the two halfnaked girls to himself. He held them close to his chest and alternated looking between them. They were looking at him too, their eyes heavy and tired and eager, heat drunk. Their breasts squishing into his chest like glorious fleshy balloons. The heat radiating from the three of them could start a fire.

That was when he realized that it had not just been acid in the pill, viagra probably played a heavy part.

They were al just so hot. It felt amazing.
"Who's first?" He half croaked out. Mabel pushed against her brother and Pacifica until she was pretty much on top of her brother, she straddled him, one strong leg one either side of his waist. She leaned forward until his face was cushioned between her impressive fatty boobs.

He began to motorboat his sister, faster and faster, the sweat mingling on his face began to almost form a lube around his face. He pulled himself out gasping. She was also gasping and laughing a little at the bizarre feeling that it gave her. She smiled down at him and began to kiss him hard on the lips. Her lips pulling up into a smile, he felt the remains of her braces still on her teeth. They made her face sparkle with the light that they left on.

She began to move her face slowly down his chest and abs, he groaned and ground himself into the bed cloth. It stopped and he craned his neck up and saw that she had stopped in front of his zipper. She slowly, sensually began to pull the zipper downwards. She kept looking between Dipper and Pacifica, her eyebrows wiggling and her tongue coming out, she then roughly pulled his pants down. He kicked a little and launched them across the room, they thumped onto the wall next to a poster of a boy band that was making a comeback.

Mabel popped his underwear down and he was released in front of them. The viagra and acid had done some impressive stuff to him. His cock was at full attention, he did not think that he had ever been full of that much blood. Mabel gasped in happy surprise. She then took as much as she could in one hand and gave a single good pump. A little bit of precum began to form on his tip, three beads dribbled from his head and began to pool down his shaft. It was tall and strong with a little bit of a tilt at the top, his head red and hot.

Mabel took the tip into her mouth and stuck her tongue out, she slurped loudly, as if to tell them what she was doing. She began to pump downwards with her dominant hand and also bobbed her head downwards at the same time, most of her actions was covered by her hair that hung past her shoulders, covering her face and the majority of his dick, he could make out a sliver of it from where her brown hair did not cover it. Dipper growled his pleasure from the very depth of his chest. Like a cold.

"Hey don't forget me." Pacifica said, she moved herself over Dipper and he saw that she had removed her pants and underwear. Her pubic hair was perfectly cut into a landing strip, also blonde, dyed or natural he could not tell. She was dripping a little, she had orgasmed once from her fingers. Dipper intended to help her out as much as he was capable of. She slowly descended, her magnificent cheeks popped out in preparation for him, she sat down onto his face and arched herself backwards as he tentatively pushed his tongue into her folds. He moved past them and found a hard little nub. He began to suck at it, and pulled as much of her into his mouth as was possible.

She almost screamed from how intense he was trying to pleasure her. It was embarrassing almost. She leaned forward keeping herself pushed down as hard as she could on his mouth, so that he had to choose between breathing and eating her out. She felt his arms wrap around her hips she yelped as he pushed more of his tongue deeper inside of her. It was so long, and oddly strong.

She moved her breasts down so that they rested against his lower stomach, her hair mingled with Mabel's. She breathed heavily as she looked down at her roommates head that kept bouncing on her brother's head. She huffed to get Mabel's attention. Mabel stopped for a moment and looked upwards. Her eyes were lost, cockdrunk. She smirked at Pacifica's jealous wanting look, she moved downwards a little bit, exposing his cock for Pacifica to gasp and gawk at in anticipation. The two girls began to lick and lap at it tentatively. Teasingly. Each tongue trailing around the shaft, going over every vein and twitch. Dipper moaned and the girls copied him, the tips of their tongues touching and shiver's of electricity mounting around them.

Pacifica sat up sharply and howled as another orgasm moved through her. Mabel gave another violent jerk at Dipper's cock and also massaged his balls for good measure. His first shot of the evening pumped out, it lanced through the air. It landed across Pacifica's belly and tits while simultaneously landing in Mabel's waiting mouth and getting stuck in her hair.
Mabel swallowed and hearts almost appeared in her eyes. She launched herself forward and began to lick at Pacifica's tummy and tits. They hung heavily as she panted. Pacifica began to fall backwards under Mabel's weight so that her legs ended up on either side of Dipper's head. Her cunt dripping in anticipation was ground at the top of Dipper's head.

"Hahaha. Excited?" Dipper said upwards to Pacifica. Mabel moved over her brother and began to lick at Pacifica again, she moaned happily. Dipper looked up at Mabel's impressive thighs, he pulled her pants down and ripped the tape away and he wrapped his arms around her waist and pulled her sharply down on top of him. Mabel laughed as she kept licking at Pacifica's creamy smooth skin. Dipper's nose was buried in his sister's bush. It was well groomed, made to look like a triangle with multiple intricate designs shaved into it.

Her thighs and hips were so thick, he grabbed as many loose rolls of fat that he could. He brought his hand up and slapped it down hard onto her rear. Mabel gasped, some hair getting caught in her mouth. Pacifica took that moment to sit up and kiss Mabel hard on the lips. She could taste Dipper and herself on Mabel's tongue as they each tried to get the upper hand, their tongues trying to wrestle the other to the bottom of their partner's mouth.

Pacifica's eyes rolled back in their sockets. Dipper felt Mabel's tunnel muscle's tighten in hope and anticipation. Her juices exploded on to his taste buds and Dipper drank as much as he could into his throat and stomach; He pulled himself out from underneath Mabel's twitching body. A little bit more came out and began to stain their sheets. It was then that he realized that it was made for a king size bed, they had kept their beds pushed together for a long time.

"Now who wants a ride?"

Mabel and Pacifica looked at Dipper, he looked at their bodies, full of so much life. Mabel's amazing ass shivering and clenching together. Her face and neck bright red, Pacifica reached down and took a little bit of cum that Mabel had missed, it was clinging to her erect nipple. Her areola's were much more obvious they were darker. Pacifica took the string of cum and popped it into her mouth. She smiled around her pointer finger and breathed inwards, it was salty and delicious. Her cheeks turned into a shading more reminiscent of beets.

Dipper's cock began to twitch in anticipation. Pacifica moved over Mabel. She applied a liberal slap with one hand to Mabel's rear, causing it to jiggle for a solid twelve seconds. Mabel had to push her head into a pillow and let out great guffaws of laughter. Pacifica kept moving forward her hair hanging around her like a waterfall of gold.

She crawled seductivly forward until she was nose to nose with Dipper. She got up into a crouch and aligned herself over Dipper's awaiting cock. She slowly began to fall down onto him. She stopped around halfway down. Most of the meaty monster firmly engulfed in her snatch. She then leaned to the side as far as possible and grabbed the water bottle that they had left on the bed. She took a huge swig and handed it over to Dipper, he ignored the melting pills in it and took his own swig. With a beating of hearts he sheathed himself completely into her.

Pacifica began to move herself up and down repeatedly, her butt bouncing up and down on his balls for good measure. It did not hurt as much as he expected, if anything it actually excited him more. He could feel his testicles working overtime to produce more cum to dump into her. Pacifica felt as if she was in heaven, he was tearing her insides up, and it felt as if he was pushing her stomach and other organs around, turning her into one enormous pleasure soup. Dipper's cock was stirring something primal in her.

They both let out groans and grunts of pleasure. She was amazed that she was even able to move around after how intense the show had been let alone actually screw someone.

"Oooohhhh Dip-dip-DIPPPPPPEEEERRR!" Pacifica screamed as she clenched down around him crashing herself down one more time, her butt clapping his balls together, he splattered her inside with his dick. Dipper deposited his load within her walls before howling.

Pacifica kissed him in appreciation before she was slowly toppling backwards. Mabel had gotten herself up and was crawling around on her knees, she licked at Pacifica's cunt and then Dipper's cock. His semen tasted amazing! And it being in Paccy's cunt and mixing with her juices just completed the taste. She moved until she was over Dipper.

"I want a turn with your big dipper now." Mabel said childishly, with a little lisp from exhaustion. Dipper complied and Mabel crawled backwards, his cock was beginning to fall asleep and she knew she could not have that. In the reverse cowgirl position she began to thrust the wilting member back inside of her until it came back to life again.

Their climax was faster this time. Harder and stronger. They almost felt complete, as if a couple of missing puzzle pieces were finally home. They even fit together better. Dipper reached upwards and cupped her tits, groping them hard and squeezing them until Mabel cried out to God and splattered his waist. He returned the favor. His cum oozing around the cork of his dick.

Pacifica whistled and the twins looked at her with wide open legs. Mabel crawled forward and sat down so that their cunts rubbed up against each other. His cum oozing from Pacifica's cunt and falling out of Mabel. He stood up and moved to them. He grasped Pacifica's butt cheeks to steady himself.

"Next time." He whispered as he squeezed them.
"What?" The girls said simultaneously. "Nothing."

He thrust first into Pacifica and then into Mabel. He went deep, their positions perfectly put so that he could go as far inwards as possible before pulling outwards and reentering the other. He got more grasping pleasure from them, as if they were two meat vices trying to cram as much of him into them. He touched against the very lips of their wombs. Sometimes he pulled out and teased them by rubbing the shaft along the lips of their pussies. They would join in by rocking together. He shoved himself one last time into Pacifica and then into Mabel. Depositing a final load in both before shoving his cock in-between them and shooting his remaining swimmers onto their stomachs and breasts. They began to rub against each other. Their great pillowy tits making a vague squeaking sound.

Dipper flopped backwards. The two girls moved around and laid on either side of him. They embraced him and left their dribbling waists and lower halves open to the air. The room was hotter than the theater. Dipper rolled his waist a little and sheathed himself into Mabel while also shoving as much of his free hand into Pacifica. He sealed them closed so nothing could dribble out. It was done subconsciously. As was the rest of the night where he kept switching his cock between them, pulling out a little just to spoon the other. No one felt left out.

"Okay seriously what is going on between you three? I see how you exchange looks." Wendy said dryly as Mabel flushed. In the adjoining room behind the curtain Dipper held Pacifica's waist close to his and they gave little pecks to each other's lips. They had all three gone to vacation at Gravity Falls where some friends lived and to see their great uncles for Christmas break. Of course it was hard to keep a three way relationship/fuckbuddery quiet but they were managing. Except of course when it came to Wendy.
"Can you keep a secret?" Mabel said nervously.

I own nothing Alex Hirsch owns Gravity Falls and Richard O'Brien owns Rocky Horror Picture Show. I do not own the callbacks either. Please review. Also if anyone wants to do artwork or whatever of my stories please PM me or place something in the comments. I would actually be rather flattered. Might make a sequel but you can put inspired by so and so if you want. Thinking of adding Candy and Wendy next time around, maybe that Emma Sue girl from the Road trip episode.