~~One week later~~

Your Pov
Wendy and I were being bored in the giftshop. Soos was talking to his girlfriend over video call in the living room. I was sweeping while Wendy read the "Avoiding Eye Contact" monthly.
Dipper and Mabel were out at the Diner getting everyone something for lunch.
Reliving the night Dip and I kissed made my cheeks heat up... until my thoughts drifted toward the deal I made with dad. I managed to hold off telling the twins what happened when Bill kidnapped me. Though Dipper kept pestering me about it.

Smack! "Ouch." I mumbled, rubbing my forehead.
"You okay?" Wendy watched it happened.
"Yeah, just wasn't paying attention," looking to see what I ran into: The snack machine.
"Alright" Wendy went back to reading her magazine.
Something caught my eye. The rug... it was the all seeing eye, my dad's symbol.
'Has that always been here? How come I've never noticed it before?'
Just then, Mabel barreled through the door, with Dipper in pursuit.
"Food's here!" They said in sync, triumphantly holding out take-out bags.
"Yush!" Wendy and I returned.

~~Time skip till after everyone ate~~

Mabel's Pov
"Mabel! Mabel! Are you just as excited as I am???" Y/n asked me.
"Uh duh, how can I not be???"
"Mabes, Mabes, come on, we're both thinking it." Y/n wrapped her arm around my shoulders.
"Ready....1...2...3!!"
We both took a deep breath.
"Its Summerween!!!!" We screamed at the top of our lungs.
"Oh yeah... I forgot today's Summerween," Dipper added, uncovering his ears.
I went over to him. "You'll be joining us, right?" Poking his sides.
"Ah!... Y-yes! O-of course!... Ahaha!! M-Mabel... stop! Y-y-y-you know.... I'm ticklish!" Dipper laughed in between breaths.
Dipper got up and started tickling me too.
We were both laughing until we noticed Y/n staring intently out the window.
'She's been doing that a lot lately at random things throughout the shack since Bill returned her' I thought.
I waved my hand in front of her face. "Hello! Earth to Y/n!"
"Its like Y/n's in a trance" Dipper noted.
I grabbed her shoulders and shook her. "Hey! Y/n are you in there! Can you hear me!"
She blinked, "Oh! Sorry... I was just...thinking."
"Are you ok? You totally zoned out for a second." Dipper asked.
"Y-yeah! Come on! Let's go get costumes!" Y/n smiled, linked arms with us and skipped out of the attic. I skipped along with her. Dipper happily let Y/n drag him, blushing.

~~Time skip to when Stan brought them to the summerween store~~

Dipper's Pov
Y/n and Mabel were in the changing rooms trying on different costumes. I already picked out mine: Link.

"What do you think of this?" Y/n stepped out an Athena goddess outfit. It was a long, sleeveless, white dress that reached the floor, a thin, braided, golden belt around her waist, with beading along the low v-neck. Golden fake vines adorned her arms and a golden fake wreath in her hair to top it all off.
Blood rushed to my cheeks.
"Uhm..."
"You're right, next!" She swept back into the changing room.

Mabel came out in an 50's white, short-sleeved, button up shirt, tucked into a pink poodle skirt, and a big, black, matching belt. She wore white and black oxford riding shoes, with plain white socks. A matching pink scarf was tied around her neck.
Mabel twirled in a full circle, "I like it!" She ran back into her room to change.
'Well that was random, but I guess it is Mabel.'

A minute later, Y/n came out in her normal clothes, clutching a costume I couldn't see.
"What did you decide on?" Craning my neck.
She giggled, "You'll just have to wait and see."

We paid for our costumes and went home. That's when I got a text from Pacifica.

"Hey Dip! U're coming right?"

~~Time skip~~

Still Dips'  Pov
"I'm ready!" Y/n shouted.
Mabel and I ran to meet her. I felt my cheeks heat up when I saw her costume.
She was dressed in a plain, white, t-shirt, covered by a "silver parka and jeans, with a silver circlet braided in her hair." (A/n: an excert, taken from Rick Riordan's, "The Titans Curse")
She held a wooden bow, a quiver of silver arrows slung over her shoulder.
"Wow Y/n you look..."
"INCREDIBLE!" Mabel squeeled.
"...powerful."
She smiled, "Thanks you guys! I love your costumes by the way."
"Are those real?" I asked, pointing to her bow and arrows.
"Yep!"
"Whoa! Where'd you get them?"
She hesitated before answering. "My...dad."
I grinned, "Cool" staring into her eyes.
Mabel interrupted by grabbing both of our wrists and rushing us out. "Come on! Let's go you two love birds! Before all the jack-o-melons are blown out!"

~~Time skip~~
Your Pov
We hit every house in Gravity Falls... except for one.
"Hey guys, I got invited to a summerween party. Want to go?" Dipper asked.
I shrugged, "Depends on who's throwing it."
"Pacifica Northwest"
I had nothing against her, so I agreed.
"Ok! And this time, we actually went trick-or-treating so I'm down." Mabel said.

We arrived at Pacifica's mansion and she answered the door.
"Dipper, Mabel, Y/n you made it!" Her smile flickered for a quick second before returning when her gaze fixated on mine and Dipper's intertwined fingers. We realized this and quickly let go.
"W-welcome to the party!" She let us in.

Dipper went off to the bathroom and I just silently drank punch.
'Man! Dipper looks cute in that.' I thought.
Suddenly, I was grabbed and slammed against a wall in a dark room. Dark spots danced in my eyes.
"Are you 2 dating!?" Said a familiar, yet angry voice.
"What? What are you talking about?" I replied, still in a daze.
"Are you and Dipper dating!?"
"Huh? Pacifica? Is that you?"
"Yes! Now answer the question!"
"No! Why? Do you like him or something?"
"Thats not important! Just back off of him!"
"Why!? Dipper's my best friend! And I work at the Mystery Shack so I see him everyday!!"
She let me go. "Fine, but you're gonna regret this!" Pacifica stormed out of the room.

"Where were you?" Dipper asked.
"Dip, we need to talk." I had to warn him about Pacifica.
A slow song started playing.
He held out his hand. "How about we talk ab-"
"Dipper!" Pacifica rushed over, interrupting him. "I've been looking for you everywhere! We should dance!" She took his hand before he could say anything and whisked him away.
Dipper gave me a glance of sorrow before letting Pacifica lead him to the dance floor.
I balled my fists. "She knew that Dipper was about to ask me to dance" I mumbled. Mabel came over to me with a look of corncern.
"What's the matter Y/n? Why aren't you dancing with Dipper?"
I pointed to the center of the dance floor where Pacifica whispered into his ear.
"Ooooohhhhh I'm sorry Y/n" Mabel immediately understood.
"Hey! I know what'll cheer you up!" She perked up, "Cheese and chocolate!" She held out some on a stick.
"Thanks but no thanks Mabes. I'm not in the mood."
"Ok, suit yourself" she stuffed it into her mouth.
I laughed, "you are a riot!"

Bill's Pov
I followed Y/n to the party. I made myself a bit younger, around 15 or 16. She knew what I looked like so I went as Kaito Kid. The Northwest girl was flirting with me until I saw Pine Tree about to ask Illuminati to dance.
"...hey! Are you even listening?!" She demanded. She looked the way I was looking, her eyes widen. "Excuse me"
I smirked. Perfect.

I walked up to Illuminati and asked her to dance.
"So what's your name, stranger?" She casually said.
"Its me, Y/n."
"Wait...dad? What are you doing here? And why do you look younger?"
"I needed a way to watch you without raising suspicions from Barbie doll over there."
"Well... this is kind of weird... dancing with my dad and all."
"Aw lightened up Illuminati! Just think of this as a father, daughter dance!"
She shrugged.

We danced for a more few minutes before Pine Tree came up.
"Y/n, we need to go now" He murmured through clenched teeth. I smirked. Jealously danced in his eyes.
She looked at me, "Sorry er... sir, I have to go."
Pine Tree grabbed hold of her hand, and looked around until he spotted Shooting Star. Then they left the party.

A/n: Sorry I didn't update like I promised! I didn't think that I'd be so busy over the weekend. Also delay through writer's block. I know its after Halloween but still wanted to do something for Halloween in the book. Plus, I was able to get some rivalry in there! It just wouldn't be fun without it! I can't say for sure when the next chapter will be out but I can promise that it'll be out soon!