So I want to make note of a few things:

Dipper and Mabel still had their adventures in Gravity Falls but never met Bill (so no Dreamscapers or Sock Opera incidents).

This was based off of The Forbidden Game book series by L.J. Smith. No knowledge of the book is needed (though it is a great series that I highly recommend). This fic will not be 100% like the book series though.

I will try to update weekly.

Bill didn't consider himself human, no matter how he looked. Though he had human like features, from his sharp, angular face to his pointy nose, and the meat sack he transversed Earth in was shaped like a human's, he was not. Nothing was ever quite what it seemed, and Bill was included in that.

Absently, he looked over himself in the mirror. His hair, too neon yellow to be called blond, was messy and spiky. Part of it came down to cover the empty space where one of his eyes should have been (or at least where it should have been had he been human). He raked his fingers through it, struggling to make it look at least halfway decent.

Things, after all, were about to change, and he had to look nice when that happened.

Mabel Pines felt like a volcano ready to erupt. Instead of pouring over lava, however, she would erupt with brightly colored confetti and a screech of "Happy birthday, Dipper!"

"Calm yourself," Pacifica said. She placed a hand on Mabel's shoulder and began to run her fingers through her lengthy, soft brown hair. "Dipper's going to come home. You don't want to lose all your excitement now, do you?"

Mabel sighed. "It would stink if he came home and found all the confetti already thrown on the floor." Her pointed purple party hat fell slightly. With gentle, familiar fingers, Pacifica put it back in its place. With the way the two worked so naturally together, it was hard to believe that the two girls had hated each others' guts. Now, Mabel couldn't imagine life without her.

"I know what you mean."

Mabel turned her eyes up, meeting Pacifica's gaze. The blond had a wide smile on her face.

"You should consider yourself lucky," Pacifica said with a smile. "For once Dipper isn't trying to throw you a surprise party at the same time for you."

Mabel grinned. She had made Pacifica her spy over the last few months, trying to find out if Dipper was trying to throw Mabel a surprise party. Pacifica had chatted with Dipper in class, texted him, and hung out with him. In all that time, she had found no proof that Dipper was going to try and attempt his annual surprise party for his sister. It had been a case of espionage worthy of any classic, black and white spy flick. Unless Dipper had managed to keep things so heavily under wraps that even Pacifica couldn't find it, then Mabel was going to be the only twin attempting a surprise party that year for their seventeenth birthday.

"You should feel lucky too." Mabel sniffed the air. "You're invited too."

"Does that mean I get to try your legendary cupcakes?" Pacifica sniffed the air as well and hummed. "From what your great uncle has told me, those things are to die for."

Mabel chuckled. "I wouldn't go that far."

"Oh, there's no need to act modest about it. If I were you, I would be proud."

"As if." Mabel giggled. "Your family is loaded. You could probably hire the most famous cupcake baker in the world."

"I could!" Pacifica's eyes lit up and her smile widened. She pulled her leather wallet from a pocket in her purse. "So what are your prices?"

Mabel's laugh echoed throughout the living room. Placing the confetti down, she pointed to the kitchen. "We'll have to discuss prices later. For now, I want to get the cupcakes out of the oven to give them some time to cool. After that, I might need some help frosting them. Would you be okay with that?"

"For the greatest cupcake baker in the world," Pacifica said in a faux snobby voice (with a joking tone that she never would have used years before, before she had learned to let go and live a little), "that would be an honor."

The warm, small kitchen was filled with food. From the plastic bowls filled to the brim with candy, chips, and overly buttered popcorn, to the ice cream and popsicles in the freezer, Dipper's party was going to be packed with food. Had Mabel had the time, she would have whipped up a cherry pie or two. Oh well, her brother and their friends probably already had enough food to gorge themselves on already.

As if waiting on the girls, the kitchen timer binged when the two entered the room. Mabel ran over to the oven and pulled it open, letting heat pour through the room before grabbing some kitchen gloves and pulling the freshly baked cupcakes out.

"Now remember, Pacifica," Mabel said. "We need to give these cupcakes some time to cool."

"Good," Pacifica replied, turning towards the kitchen door.

Mabel raised an eyebrow. Where had all of Pacifica's earlier enthusiasm gone to?

"Wait here," Pacifica said, and was out of the kitchen before Mabel even had time to respond.

With a shrug, she placed the tray of cupcakes on top of the stove and closed the oven door. As nice as the heat was on that cool autumn night, it made her sweat in her bright pink sweater.

A few moments later, the sound of Pacifica's shoes tapping against The Mystery Shack's wooden floor could be heard. Then, warm arms wrapped around Mabel's side and lips tickled the back of her neck.

"Happy birthday, Mabel," Pacifica said. Fingers brushed against Mabel's skin and something else came around her neck. It felt cold and slightly heavy, and its touch didn't suddenly vanish.

Mabel gasped. "Pacifica, did you make this?" She held the necklace up. Though the supplies it was made of looked rather fancy (and looked like it was made out of everything but craft store stuff), the slightly messy quality of it made it appear handmade. Mabel held the necklace up, looking over the pieces. The interlinking chain shone under the kitchen's lights, sparkling with a deep golden color. In bejeweled letters, her name was spelled out. At the end, right after the "l" in her name, there was a sparkling heart.

"I may have hired someone to help me out a little," Pacifica said, tightening the squeeze on Mabel's slightly chubby waist, "but I did make it myself."

Mabel turned around, giving Pacifica a tight hug of her own. "Oh thank you, thank you, thank you! This is the best birthday gift ever!"

Pacifica laughed, and returned the hug. "Well, I guess that made the burns from using the hot glue gun worth it." She leaned forward and kissed Mabel. It was far from their first kiss, and judging by the way that their relationship was going it wouldn't be their last, but it still felt magical. It was as if gravity itself had been turned off, and for a moment the two were floating together, entangled in the air. Happiness ran through Mabel, a happiness so deep that she could feel it in her toes and at the tips of her fingers.

The two pulled away for a moment. Pacifica was grinning and Mabel still didn't quite feel like her feet were on the ground.

"Best birthday ever," Mabel said.

Dipper Pines sometimes couldn't help but think that he was the unluckiest boy on earth. He wouldn't say that if he weren't exaggerating. Not only had he managed to go through half of the day completely oblivious to the fact that it was his birthday (and thus also his sister's), but he had also managed to get his sneakers sobbing wet from running in a puddle and nearly gotten scratched by a stray black cat. It was like his life was a terrible sitcom that never ended. With the way the terrible day had started, the seventeenth season was probably going to go even further downhill than the last.

"You had to get lost," Dipper muttered to himself. His hands were bunched tightly in his pockets. As he spoke, his breath fogged. Though it had been a warm day, feeling more like early June than late September, the temperature had cooled considerably when the sun went down. A shiver ran up his spine, sending goosebumps up his arms and down the back of his neck.

Though he and his sister had lived in the small town of Gravity Falls since they were twelve, he didn't recognize this part of town. Had the town not already been so strange then he would have been tense, even afraid. Instead, Dipper was frustrated with a capital "F". What kind of a guy forgot about his own sister's birthday?

Dipper apparently.

He had ended up spending half the day looking for a present for Mabel. Once school had ended, he had gotten on his bike and driven to every store he could think of. When that had failed, he had dropped his bike and heavy backpack at home before racing into the forest to look for something mysterious. That little adventure had proven fruitless, and a Dipper had simply left with scratches from stray tree branches and mud covered shoes.

He hadn't even managed to get out of the right side of the forest. Instead, he had ended up in this dark side of town. The street lamps were dim, the road was worn with pot holes and most of the buildings looked to be abandoned and forgotten, and the sidewalk was heavily cracked. With his luck, he would probably get a call from his father saying that their mother was in the hospital with a broken back and he and Mabel had to rush down to California right away.

Dipper's eyes scanned the place, looking around. His legs ached from their constant use and his teeth were beginning to chatter. This looked like a part of Gravity Falls that had simply been forgotten. Considering no other store had something that seemed like the right gift for Mabel, why would this place have anything? It didn't even have anything open. He doubted that his sister wanted an old and dusty closed sign. He considered heading to town and just picking up a gift card; it would be as good of a present as any.

That was when his eyes saw the light. For a few moments, he blinked at it, unsure of what he was seeing. Once his vision cleared, he began to walk towards the small brick building at the end of the road with dimly lit windows.

The closer that Dipper got, the more that he saw. A hanging sign read "All Fun and Games" in carved wooden letters. There was a mural painted on the brick wall, though the paint was slightly faded. It showed a group of happy children, probably less than ten or eleven years old, playing board games. There was an almost creepy look to them, like those overly enthusiastic kids in fifties ads. In the middle of the mural was a door. The metallic feel of the faded brass handle felt a bit strange, almost as if Dipper had expected it to be painted as well. But it was solid, and opened up to a small shop.

There wasn't much to see. Other than a few tables and chairs set up in the center of the room and a few shelves around the walls, the place was empty. The cash register in the back looked faded. Board games sat on top of the tables, with pieces stuck on random spots, as if the players had left the board in the middle of playing.

From hidden speakers, slow music played throughout the room. The carpet was a bland grey color, like the kind in schools, and the walls were a light tan color. Though the place seemed clean and simple enough, lacking the dust and wear that the other buildings on the block had shown, a feeling of something old hung thick in the air. Dipper was sure that he was imagining it, of course. The place had to be new or eventually Mabel would have dragged him over. After all, she loved games.

Dipper's eyes widened, taking in the room surrounding him. Why hadn't he thought of it sooner? A game, or games considering how much Mabel loved them, would make a great gift. Oh, he could see her face lighting up already. He rushed over to a shelf and began to look the store's wares. The games looked to be from all over the world, everywhere from China to Brazil to Germany to the United States. Some were new, with brightly colored boxes, while some games looked to be ancient. Dipper picked up a Monopoly box. Though the box's colors were faded, it was in such great condition. It had to be in mint condition, and looked to be at least fifty years old (if not far older). The price tag was even more shocking, with it being a mere fifteen dollars.

You lucked out, Dipper. Dipper grinned at his thought. For once, things were starting to look up. It was as if the day was trying to make up for how terrible it had been earlier.

He looked over other shelves, taking whatever he thought Mabel would like. Rather than getting her one big, expensive gift like he had originally planned, he could get get her a bunch of gifts. Surely that would make her smile.

By the time he had found his fourth game, his arms were loaded.

"Need a little help with that?"

"Huh?" Dipper turned around, meeting eyes with a blond haired worker looking to be about his age. His eye was a deep brown, with a few flecks of gold in them. His hair covered his other. He was taller than Dipper by a few inches and slightly muscular. For a moment, Dipper couldn't help but run his eyes over him.

"Sorry to surprise you," the guy said. He was dressed in a black polo and khaki shorts. A name tag read "Bill C." on it. "I just noticed that you were carrying around a lot."

"Oh, some help would be great." Dipper smiled. "I was about to carry this to the cash register to pay."

"How wonderful!" With little effort, he took the games from Dipper's hands and walked over to the cash register. "So are these for you or are they gifts for someone else?"

"They're for my sister." Dipper tended to be on the introverted side. However, there was something about this guy that made Dipper feel a little more chatty than usual. "It's her birthday today."

"How wonderful!" He smiled. "Tell her I said happy birthday."

Dipper nodded. "Of course." He almost wanted to turn silent, to pull out his cell phone and see if his friends or sister had texted him anything. Instead, he spoke on. "It's actually my birthday today too."

The worker raised an eyebrow. "Now how would that be?"

"It's a twin thing."

"How delightful!" Bill winked with his one visible eye. "And a happy birthday to you!"

Dipper felt his cheeks go hot. "Thank you."

"Would you like these gift wrapped? It's free of charge."

"That would be great! Thank you so much!"

Bill smiled back. "It's nothing. Now who am I making this gift out to?"

"Mabel," Dipper replied.

He picked up the games and turned into a back room. The door shut with a bang behind him. He came back less than a minute with the boxes in hand, all neatly wrapped in different colored and patterned wrapping paper.

That was fast, Dipper thought. Like magic or something.

This time, there was an extra box. It was plain white and not wrapped.

"What's that?" Dipper asked, raising an eyebrow.

"Just a little gift, free of charge." Bill winked again. "Just my own little present for the birthday boy."

Dipper's cheeks went red again. "Thank you so much."

"For you," he replied, "anything. Anything in the world." His eye looked intensely at Dipper for a moment, as if he was trying to take everything that he possibly could in about him. He then placed the boxes in a large plastic bag and handed them over to Dipper. "I hope that you and your sister have a splendid birthday."

"Thank you," Dipper said.

"Have a nice night," Bill replied before waving goodbye. Dipper gave him a quick wave back before leaving.

It was only when Dipper was outside that he realized that he hadn't paid. He turned to open the door, but found it locked. After knocking a few times with no answer, he turned and left. Frankly, he was getting quite sick of those kids' painted faces looking at him.

Once he had walked a good deal away, he pulled the plastic bag open. His hand was drawn towards the white box, so blank and yet looking like it could hold so much. It was Dipper's birthday present, an unwrapped box that held a mystery all its own.

Instead of opening it, however, he looked to Mabel's gifts. They were beautifully wrapped, far from the messy work that Dipper would have done had he wrapped it himself. There was a reason that birthday gifts usually came in gift bags. He looked over the name tags for a moment. In looping script, the words "To: Mabel, With love from: Dipper" were written.

He froze. For a moment, Dipper searched his mind, but always came to the same result.

He was sure that he had never told the worker his name.