A/N: Ages for the characters in this story is all switched up so I'll be posting the ages along with the story.

Mason Alexander "Dipper" Pines is not like any typical college student, although he does pull an occasional all nighter while hopped up on Blue Bison* Energy Drinks to study for an exam, but that's about it. He also has a job helping out his Great Uncles Stanley and Stanford (Ford never went through the portal in this universe) at their family run attraction called, "The Mystery Shack."

He currently lives in a 2 bedroom apartment with his girlfriend, Pacifica Northwest, in the town of Gravity Falls, OR. They only needed one room to sleep in, but Dipper decided he could use the other room for storage. Just now he was opening the door to his apartment to see his beautiful girlfriend sitting on the couch waiting for him.

"Hey there sweet thang," said Pacifica.

"Hello your self beautiful," said Dipper, "You know what day it is right?"

"It's Friday," said Pacifica, "Does that mean what I think it means?"

"Oh yeah," said Dipper.

Ten minutes later.

"I'M GONNA OWN YOU NOOB!" yelled Pacifica while holding a game controller.

"Nice Try sweet heart but this game is my life," said Dipper.

The TV makes an explosion sound.

"Game, The winner is..... Pacifica," said the Guy in the video game.

"OH! Suck it grandpa," said Pacifica.

"Hey, I'm only 4 months older than you," said Dipper.

"Oh yeah, what are you going to do about it, throw your adult diapers at me old man?"

"No, you might get attacked by the tickle monster."

Dipper then starts to tickle Pacifica making her laugh uncontrollably.

"Okay I give I give," said Pacifica.

Dipper stops tickling her.

"Phew if you did that any longer I would have wet myself," said Pacifica.

"Who need the adult diapers now?" Dipper asked sarcastically.

"Oh shut up!"

Just then Dipper's phone starts to ring. He picks it up.

"Hello Dipper Pines speaking," said Dipper, "Oh, I see, what happened? Okay I'll be there bye."

Dipper hangs up.

"What happened?" Pacifica asked.

Dipper lets out a sigh.

"My parents are gone," said Dipper.

"Oh, I'm so sorry," said Pacifica.

"It's okay."

"If you don't mind me asking, what happened?"

"They were in a deadly car crash."

"Oh my God."

"The funeral is in Oakland Monday."

Monday came by fast for them. The funeral went by fast. Right now Dipper is in the reading of his parents will. (I don't know what the place is called so just roll with it.)

They were finishing up on everything and just getting for the lawyer to say the final will and testaments.

"Alright lastly," said the lawyer, "To our oldest son Dipper we leave you the responsibility of raising your little sister, Mabel Ariel Pines."

"What I don't know how to raise a kid," said Dipper.

"They trusted you the most. They know how much you and your sister get along."

On the way back to Gravity Falls Dipper and Pacifica were driving back when a certain song came on the radio which reminds him of the times he spent with his little sister. (Listen to the song up above when reading the flashbacks)

Here comes the flashbacks.

He remembers when she first came home:

He was so happy to become a big brother.

"Can I hold her mom?" a young Dipper asked.

"Sure little buddy," said his mom.

His mom hands him a little baby girl wrapped in a pink blanket.

"Hi there Mabel I'm your big brother," said Dipper.

Infant Mabel looks at Dipper and gives him a smile which makes Dipper smile as well.

He then remembers when Mabel spoke her first word:

"Come on Mabel can you say Mommy, Mom-my?" said their mom.

"How about saying daddy? Dad-dy?" said their dad.

Dipper walks in the house.

"I'm home from school," Dipper announced.

"Dipper!"

Their parents look at their daughter. Dipper comes running up to her.

"What did you say?" Dipper asked.

"Dipper," said Mabel.

"I'm her first word."

"Doesn't surprise me there, she loves you," said their mom.

Dipper gives Mabel a hug.

"Wuv ooh Dipper," said Mabel

He remembers when she had a monster in her room: (This is when Dipper became the 12 year old we all came to love.)

A screaming Mabel comes running into Dipper's bedroom.

"What's wrong Mabel?" Dipper asked.

"There's a monster in my room," said Mabel, "I think it's after my dollies."

"Hey don't worry baby sister I can get rid of that monster."

"How?"

"Follow me."

They walk into her bedroom with Dipper carrying a flashlight.

"Alright where did you see the monster?"

"I think he is in my closet."

Dipper checks the closet.

"Nope there's no monster in here."

"Check under the bed."

Dipper checks under the bed.

"There's no monster, but, I did find something under here."

He pulls out a Elmo plushie.

"Elmo!"

Mabel takes the plushie from her brothers hands.

"Thanks for getting rid of the monster big brother."

"Anytime little sister, anytime."

And he remembers the when he first left for college:

"Don't go Dipper,' said Mabel as she was tugging at his pant leg.

"Sorry Mabel, but I have to go," said Dipper, "I have to go to college, I'm planning on making this world a better place for you."

"But I don't want you to leave me."

"I'm not going to be gone forever I'll be back."

"How?"

"Because we're brother and sister and nothing is going to break that bond."

"You better promise you'll come back."

"I pinky promise."

They made a pinkie promise and hugged.

"Don't forget about me big brother."

"I won't little sister."

Flashbacks over.

Today was the day Mabel is expected to come.

Dipper had some time off from school because it was semester break.

He was putting the finishing touches on Mabel's new room when he heard a buzzing noise.

"Who is it?" Dipper asked.

"It's your landlord I got a girl here she said she wanted to see you," said the landlord.

"That's my little sister just send her up."

"You got it dude." (Full House reference)

Dipper waits by the door of his apartment waiting for Mabel to come up. He hears a knock on the door and looks out the peephole to see a girl with a red headband, a red sweater with a shooting star on it, a purple mini skirt, and black ballet flats carrying 2 pink suitcases and a pet carrier. He automatically knew this was Mabel.

He opens the door to Mabel running in and immediately hugging him.

"I missed you big brother," said Mabel.

Dipper smiles and hugs his sister back.

A/N: Hope you guys liked the first chapter. The song above helped me think about what "Big Brother Dipper" would do for his little sister, plus I really love that song. I have an older brother myself so I know what it's like to have one. Okay see you next chapter.