On the sunny day of Gravity Falls, Stan was driving in his car with the triplets sitting in the back seat. Dipper was reading a book, Mira played a videogame, and Mabel was eating a bag of chips. She took two chips and placed them on both of her ears.

Mabel laughed before saying, "Nacho earrings! I'm hilarious!"

"Eh, that's debatable." Stan said, before honking on the car, "Aw come on what's with all this traffic? And why is it all-"

Stan saw before him that there were covered wagons on the road. Stan had begun to panic, "Oh, no! No! No! No!" He pressed on the gas pedal causing the triplets to be pushed back in their seats, "Not today! Not today!" He shouted as he drove.

"Grunkle Stan what's going on?" Dipper asked holding onto the door handle.

"You look like you've seen a ghost." Mira said holding onto her seat.

"No time to explain!" Stan said, driving as fast as he could, "We gotta get out of here before it's too late!"

The car came to a sudden halt when the covered wagons had circled around the car.

"They've circled the wagons!" Stan exclaimed, "We're trapped! NNNNOOOOOO!"

Mabel looked out the window, and saw a cow; it mooed at her as if to say hello. "I have a good feeling about today." Mabel said to her siblings.

They had gotten out of the car, and saw that the whole town was looking old fashioned and such. "Man look at this place." Dipper said, comparing the town to a postcard.

"Dirty glass!" One of the townspeople shouted, "We got Dirty glass here!"

"Okay, I'm lost." Mira said, "What exactly is going on?"

Stan had explained, "It's Pioneer Day. Every year these yahoos dress up like idiots to celebrate the day Gravity Falls was founded."

Toby Determined walked up to the Pines, dressed like one of Pioneer's back in the day and said, "Welcome to the year 1863!"

"I will break you little man!" Stan yelled raising his fist.

This had caused Toby Determined to run away as fast as possible. The triplets continued to look around the town that people were selling.

"Oo! Candle dipping!" Mabel said.

"No way!" Dipper said, "Gold panning!"

They looked over at a priest who was just pronouncing marriage to a man and his woodpecker. "Is that man marrying a bird?" Mira asked.

Dipper took out his journal and flipped through the pages, "Hang on, I remember this. It says here, Gravity Falls used to have legal marriage for marrying woodpeckers."

"So… It's illegal now?" Mira asked.

The man the married the woodpecker had overheard the triplets talking to one another. He walked up to Mira and said, "Oh it's still legal. VERY legal." With that, the man walked away. They soon heard some say over the speakers, "Come one and all to the opening ceremonies!"

"Sounds neat." Mira said before turning to her siblings, "Let's go check it out!"

"Sure, why not?" Mabel said, "It sounds fun."

Dipper turned to Stan, "Aren't you coming Grunkle Stan?"

Grunkle Stan replied, "No thank you! Just remember if you come back to the Shack and start talking like these people, you're dead to me!"

"There's a carpetbagger turnip cellar!" Dipper said talking like a pioneer.

"Well hornswabber my haversack!" Mabel said, closing one eye.

"That just ruffles my chicken feathers!" Mira said, making it look like she's a chicken.

All three of them spit on the sidewalk; The triplets laughed as they ran down the block. "DEAD TO ME!" Stan shouted to them. The triplets ran into the crowd, to see what was happening up on the stage. They saw Sheriff Blubs up on the stage.

"Here ye! Here ye!" Blubs said, "Ye olde commencement ceremony is about to begin!"

"Woo! I got a bell!" Durland said while ringing the bell. Though they seemed to have not taken notice when a woman's purse was stolen.

"Ring! Ring!" Durland cheered, "Whoo!"

"He sure loves his bell." Blubs said.

The triplets from where they stood, were surprised to see Pacifica and her parents come onto the stage; She took the microphone, "Howdy everyone! You all know me! Pacifica Northwest, great-great granddaughter town founder-Nathaniel Northwest. I'm also very rich."

The clapped and cheered; except for the triplets.

"Now if you've got the pioneer spirit, we ask you to come on up and introduce yourself!" Pacifica said.

Mabel gasped at this, "Audience participation!"

Dipper and Mira had an unsure look on their faces, "I don't know, isn't she your arch-enemy?"

"Yeah, I thought you said you didn't like her." Mira added.

"That's all water under the bridge guys!" Mabel said to her siblings before running to the stage.

"Our first newcomer is…" Pacifica said before saying angrily as she saw Mabel come up on the stage, "Mabel…"

Mabel said to the crowd, "Yeah! Let's get this Pioneer Day started! Right guys? USA! USA!" Everyone in the crowd chanted USA with Mabel; One man in particular was crying with joy as he chanted USA with the crowd.

Pacifica walked over to Mabel, "I hate to break it to you, but Pioneer Day is for serious people, and you look not to mention act ridiculous." She pointed to Mabel's sweater, "I mean, a puppy playing basketball? Are you always this silly?"

Dipper and Mira started to worry about Mabel as they saw a hurtful look on her face. She glared at Pacifica, "Hey! I'm not always silly! I can be serious!"

Pacifica laughed out of amusement, "Your earrings are made of nachos."

Mabel looked at her nacho earrings and blushed out of embarrassment. "Give her a hand everybody!" Pacifica said to the crowd. Dipper and Mira saw Mabel run off of the stage with tears in her eyes; they both quickly ran after her, pushing their way through the crowd. They had found her, sitting under the Nathaniel statue. The two of them sat beside her; Mira sat on her left side, while Dipper sat on her right.

"Are you okay?" Dipper asked.

"I need some old-time butter scotch." Mabel said.

Mira handed her a piece of candy and Mabel took off the wrapper and placed it in her mouth.

"Mabel, don't let what Pacifica said to you to heart." Mira said, rubbing her back comfortable, "She's just selfish that's all."

Mabel let out a sigh, "Dipper, Mira? Can I ask you guys something?"

"Of course you can." Dipper replied.

"What is it?" Mira asked.

"Do you guys think I'm silly?" She asked them.

Both Dipper and Mira looked Mabel nervously. Mira played with her braid while Dipper rubbed the back of his head. "No?" They both said awkwardly.

Mabel groaned at this, "I knew it! I thought I was being charming but now when I really think about it… People see me as one big joke." Mabel removed her nacho earrings and than her sweater revealing a light purple short sleeved; she tied it around her waist,

"Mabel, what are you doing?" Mira asked with concern, "You love that sweater."

"I did before Pacifica ruined it!" Mabel said, "She ruins everything!"

Dipper looked over where Pacifica stood; she was still up on the stage. "Pacifica!" He said with a glare, "Why in the world does she think that being related to the town founder means she can treat everyone like garbage? Someone needs to take her down a peg."

As Mira comforted her sister, it wasn't long till a certain something came to the top of her head, "Hey Dipper? Didn't your journal say about her great-great grandfather?"

This certain thing came to the top of Dipper's head too, "Hey yeah, I think it did!" Dipper took out the journal from his vest and flipped through the pages of it until he stopped at a certain.

"Ah-ha!" He said, "Here it is! Do you guys want me to do the voice or uh-"

"Just read normally." Mabel and Mira said in unison. "Right okay." Dipper said. He sat down in between them and read aloud what was written while his sisters looked over his shoulders.

"In my investigations I recently made a discovery. National Northwest may not be the true founder of Gravity Falls! I believe this secret is buried somewhere somewhere on the enclosed document. If only I could crack the code."

The spotted the folded document inside the journal. Carefully, Dipper removed it from the page. They looked over the document. "Guys…" Mira said, "Do you realize what this means?"

"If this cover-up is true than it would mean Pacifica's whole family is a fraud!" Dipper said, "This could be a major conspiracy!"

"Really?" Mabel asked with a tilted head.

"Don't worry, I'll investigate this!" Dipper said standing up.

"Count me in." Mira said with a smile, "You could sure use the help!"

"In that case, I'll help too!" Mabel said, "Conspiracies are super important right?"

Dipper and Mira nodded their heads in reply.

Mabel said to them, "Well, if I help you guys crack the code, then nobody could call me silly ever again!"

"That's the spirit Mabel!" Mira said.

"Than it's settled!" Dipper said putting his hand in the middle of his siblings and himself, "Mystery Triplets?"

Mabel and Mira looked at him with confusion. "What?" He asked.

"I thought you didn't like that name?" Mira said with a quizzical look.

"Yeah, why the change of heart?" Mabel asked.

"It grew on me." Dipper said before asking again, "Mystery Triplets?"

Both of his sisters smiled, and put their hands on top of heads, than shouted loudly to the sky as they lifted their hands high into the sky, "MYSTERY TRIPLETS!" With that being said, they headed towards the library. From behind the statue however, Sheriff Blubs was watching the Pines triplets from a distance. He took out his walkie and contacted someone.

"This is Sheriff Blubs!" He said, "We've got a code sepia!"

"What!?" Someone on the other side of the walkie exclaimed, "What are you doing about it!?"

"I'm following them right now."

"Find them and stop them. There is no room for error."

"I understand. Blubs out."

He turned off the walkie and turned to Deputy Durland. "Deputy Durland, maintaining this cover-up is the mission." He said, "We've been training for this for our whole career. Are you ready?"

Durland cheered as he rang the bell; Blubs couldn't help but laugh, "If being delightful was a crime, you'd be breaking the law."

"Let's go get'em!" Durland said, and thus they headed in the direction the triplets had gone to.