For: @AishoTheFangirl

Request: "Reader wants to celebrate Bill's Birthday and throw a surprise party, but has to figure out when his birthday is and has to be stealthy-ish, because Bill hinted that he doesn't like his birthday and he doesn't ruin the surprise by finding out."

A/N: Now fair warning: This will be a three-part short story and I will post the other parts whenever they are completed. I did do my own little spin on this request so I hope this is still to your liking, Aisho. Hope you enjoy! (This was actually extremely fun to write, I miss writing Gravity Falls so much!)

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"Wow... I never thought I'd see the day where I was invited to a birthday party that had a live elephant performance, a backyard fireworks show, and had every gift bag filled with a puppy for the guests to keep and take home," I spoke my thoughts allowed, shocking myself that a sentence like that just came out of my mouth as I hugged the small Siberian Husky close to my chest.

"I suppose that's what happens when we finally get to be on good terms with Pacifica and she decides to invite us to her 'Birthday Extravaganza,'" Dipper pointed out, petting the top of his Beagle's head.

It was around 1 am in the morning now, and the Pines, Bill, Markus, Neal, and I were finally heading back home from Pacifica's 17th birthday party. All in all, it wasn't so bad of a night. Sure, the older rich folk despised our presence and looked down at us like we were rats that belonged in a sewer, but Pacifica seemed really happy and relieved at the fact that we made it. And in the end... that's all that mattered to me. The rich can look down at us all they want, I don't care. If we are able to make our friend happy and help her to enjoy her special day then all those dirty looks we received tonight had all been worth it. We gave her the birthday present she really wanted this year and it wasn't some pony or a new $1000 dress, but instead all she wanted was a night where she could hang with some friends and make some new memories while we fooled around and made the most of our time together. I think it's safe to say that her birthday ended up being an absolute success.

"Y'know, I was almost certain her parents were going to kick us out of there after you two idiots decided to take a dive into the chocolate fountain. Just because the chocolate fountain was so big that one could jump inside of it did not mean that one should jump inside of it," Dipper continued as he turned to scold the two dream demons who were covered in chocolate from head-to-toe.

Bill Cipher threw his hands up in defense with a playful smirk spreading across his lips. "Oh Pinetree, would you calm down? Daggers and I were just having a bit of fun! It could've been a whole lot worse, mind you. For example, someone could have easily died. Usually there's a stack of corpses piled up in the corner of the room at the end of every party that I've either hosted or have been invited to. You're lucky we chose to be a bit more behaved and settled on taking a midnight swim instead~"

"Which, by the way, was really fun and also very delicious- you guys should have joined in!" Markus exclaimed as his Newfoundland pup began to lick some of the chocolate off of his fingers. I simply rolled my eyes in response, trying to hold back the laugh that wished to escape.

"...Look, I'm just saying- if you want to do that kind of stuff at the parties you throw then go right ahead! But this was Pacifica's party and you guys could've ruined it for her if we got kicked out."

"...But we didn't!" Bill retaliated, his smug expression still holding strong. Dipper let out an exasperated sigh, too tired to keep fighting with my demonic boyfriend.

As we were nearing the Mystery Shack, a small thought made its way into my mind. A small thought that began to grow bigger the longer I started to ponder about it. With my curiosity getting the better of me, I turned to Bill and began to speak my thought aloud to him, "We've been dating for awhile now, and I don't think you have ever told me when your birthday is. I've never even heard about a birthday party being thrown for you here in Gravity Falls. And you've been here now for... what- two years? Why might that be?"

For a split second, I could have sworn Bill's eyes had widened and he appeared to look startled due to my question- but just like that, the split second passed and he was back to his smug appearance as he shrugged and turned away to look ahead once more. "Probably because I don't celebrate my birthday. It's not that important to me. I've been alive for at least a trillion years, maybe even longer-... I'm not too sure actually how old I am; eventually you just start to lose track of time once you get to be my age. You really think that after all these years I still care to remember the day I was born? Besides, birthdays are just meant to be reminders that another year has passed and you are just one more year closer to your grave. I don't see much of a reason why anyone would want to celebrate that."

I stared over at him surprised, not sure how to respond. I ended up just giving him a single nod before I decided to stay silent the rest of the way home. It... honestly did not make any sense to me. Bill Cipher was an attention seeker, he loved to have the spotlight on himself at all times. He was also a party demon whose life source depended on attending parties and going wild. Now what better way to combine those two things then for Bill to throw himself a birthday party every year? A day where all the attention is on him and he gets to party like there's no tomorrow- until tomorrow eventually does come and his birthday has finally passed. But he doesn't! He doesn't celebrate his birthday and that confuses me! Why pass up the chance to have a special day that's meant to celebrate him and him alone?

Something just... doesn't add up. And the longer I laid in my bed thinking about it, the more I felt determined to figure out when Bill Cipher's birthday was and why he has been trying to avoid it.

Turning my head to glance at my alarm clock that sat on my nightstand, I saw that it was now 4:54 in the morning. With my thoughts racing like this, I knew there was no chance that I would find myself being able to fall asleep. Might as well get to work now.

I got up and stretched, maneuvering around the sleeping Husky that was curled up on the floor in a makeshift bed—that I made for him out of spare blankets—before heading out of my room. I was in search for answers, but where was I going to receive those answers? I honestly wasn't sure, but I had to start somewhere. I kept walking down the hallway until a particular door came into my line of vision. Well, I did say I had to start somewhere... Seeing as Bill hasn't told anyone in this realm about his birthday, maybe someone who came from his dimension might know about it.

I walked up to the door and began knocking on it. I stood there for a couple of minutes, continuously knocking to no end until finally the door opened to reveal an exhausted-looking Markus Locke who just so happened to be shirtless and wearing a pair of grey sweatpants. His hair was also slightly damp; I'm guessing that would be because of the shower he had to take to get all of the chocolate off of his body.

"...Sweetheart, do you have any idea what time it is?" Markus slurred out his words, leaning against the open door as he rubbed his eyes in a tired manner.

"I am well aware of the time, Locke. I'm here because I can't sleep due to a question that has been nagging at me ever since we got back."

"Okay... but why do you need your question answered now? Couldn't you have waited to ask me in the morning after I had gotten a good nights sleep?!"

"Yes, you're right, I could've done that... but I'm way too impatient to wait that long." Markus groaned in response to this, crossing his arms and awaiting for me to continue. "I want to know when Bill's birthday is, and I was hoping that maybe you might know...?"

Markus raised an eyebrow, looking down at me skeptically. "Y/n... do I look like I memorized the bibliography of Bill Cipher on my spare time? I have no clue when his birthday is! As far as I'm aware, I've never seen Bill tell anyone when his birthday is."

"But don't you think that's strange? It doesn't make sense to me... There's gotta be a reason as to why he doesn't celebrate or even talk about it, right?"

"I don't know, Y/n, you're asking the wrong demon," Locke muttered as his eyelids began to flutter shut, leaning against his door more for support.

I thought about what he said for a moment before snapping my fingers, causing the powerless demon to jolt back awake. "I AM asking the wrong demon! Oh my gosh, why didn't I think of this sooner?! Do you know where Pyronica, Keyhole, and the others live?!"

"Wha- Uh... yeah...?"

"Great! You can take me to their place so I can interrogate them to see if they know anything about Bill's birthday!"

"I guess I could... Umm... We'll leave around noon, how does that sound?"

"Yeah. No. We're leaving now, so get changed."

"What?!" Markus screamed, throwing his hands up in the air while nearly falling over in the process of letting go of the door. "Why?! Why at 5 in the morning- and why me?! What did I do wrong to deserve this punishment?!"

"Punishment? It's not a punishment- Look, if you help me out with this... I'll-... I'll do all of your chores for a whole month."

The demon froze, staring at me with wide eyes as he now seemed to look more awake and alert after my words reached his ears.

". . . Let me go get a shirt on."