Summary: At five years old, the Pines Twins are bored with their regular toys. So instead, they decided that they're going to make an imaginary friend to play with. So they 'create' Bill and of course, nothing but trouble comes from it.

Imaginary Friend

"I'm bored." Mabel whines as she flops to the ground next to her brother.

Her brother, nicknamed Dipper, sat in a beanbag chair looking through his favorite picture book. He closes the book and nods his head as he gently puts his book down. Dipper agrees with his sister's feelings, as even his favorite book can't seem to get rid of the bored feelings that just won't leave him alone.

"Wanna play hide and seek?" He suggests.

"No, you always cheat." Mabel pouts.

"Do not!"

"Do too!"

"Do not!"

"Do too!"

"Kids!" A voice calls from down the hallway; it's their babysitter Lauren. "Keep it down, I'm on the phone!"

Moments later they hear the teenage girl laughing on the phone again and the twins make identical face at each other to show their dislike of their babysitter. They giggle, quietly, and go back to trying to figure out what to do.

"Drawling?"

"I'm drawed out."

"Tag?"

"Lauren will yell at us for playing inside."

"Checkers?"

"No."

"House?"

"Nope."

"Dolls?"

"They're action figures, Mabel!"

"Psh! Video games?"

"Mom took the game system away, remember?"

"Oh yeah…"

The twins sighed and laid on their backs side by side.

"I wish there was someone here to play with us."

Dipper shot his sister a hurt look.

"Besides you Dipper, you're always with me. I mean, like someone cool and who actually plays with us! Like, like, James!"

At the mention of their past babysitter, both twins sat up and smiled at each other. James was so different from Lauren. Instead of just shoving them in a room and telling them to be quiet while they talked on the phone the entire time, James had actually sat down with them and played with them. The Twins had loved him and when he had moved, they had cried and begged him to stay. They had even promised him that he could stay in their room if he wanted. But sadly, the twin's parents had explained to them that James' parents would miss him real bad if he didn't go with them, so the twins tearfully had said goodbye and watch their best babysitter leave.

"Yeah, someone fun." Dipper spoke softly, thinking of James. "Someone who actually spends time with us."

"Oooh, they gotta be spon-spon-spon…random! They gotta be silly too. Because silly is funny."

"They gotta listen to us, a-and they gotta believe us too when we tell them stuff."

Again, the twins scowled in unison as they thought of their parents not believing them about Lauren.

"They gotta like to play games too."

"Maybe tell us stories too?"

The twins suddenly felt a very strange sensation in their bodies. They felt lightheaded and unable to suddenly stand. They collapsed on the ground, but luckily not too hard. They held hands and a strange growing warmth grew between each other's touch but neither of them let go. Suddenly it felt like the warmness had sprung out of them and the strange lightheadness was gone as well. Blinking open their eyes, the two five years olds blinked when there was a strange glowing object in the middle of the room, floating nonetheless.

"Wow, Pine Tree and Shooting Star! I never thought I'd get to meet you so soon! You two sure tapped into your potential early and you're only littles! I can only imagine what you're gonna be like when you finally make it to Gravity Falls."

The floating and glowing (was it actually glowing or just a really bright yellow? The twins weren't sure) triangle, yes the twins knew their shapes thank you very much, somehow seemed to be talking to them. The two stood in wide eyed awe of the floating triangle though, and they didn't really take in what the being had said.

"Wow!" Mabel gasped with wonder as she took a step forward. "Who are you? What are you doing here? Are you a fairy?"

The floating triangle blinked its giant eye at them before reaching up and taking off its top hat and bowing at them theatrically.

"My name is Bill Cipher, and I'm here dear children, because you two summoned me!" The newly dubbed Bill put his hat back on and looked at the twins curiously. "Now, why did you two summon me?"

"Summon?" Dipper parroted, looking at his sister who had the same look of confusion.

"Yes, summon. It means you two called me here…Though, it seems that you didn't call me the usual ways. What were you kids doing before I appeared here?" Bill circled the twins in the air, making the twins whirl around in circles to watch him.

Bill giggled when Mabel nearly fell over from being dizzy and she had to cling to Dipper to stop from falling over.

"Well, we were talking about James!"

"James?"

"Yeah, James! He used to be our really cool babysitter but then he moved away and now we have a super stupid head babysitter, Lauren." Mabel explained as Dipper nodded rapidly.

"Wow, how horrible." Bill chuckled as he went along with their conversation.

"It is!" Dipper cut in, "Our parents think we're just making stuff up, but Lauren just sticks us in our playroom and just talks on the phone the entire time! Plus she can be mean." Dipper pouted and Bill had to stop himself from squealing at how adorable the kid looked.

"So," Mabel cut back into the conversation seeminglessly, and it was obvious the twins were used to sharing their words along with their toys. "We were wishing someone was here to play with us! And here you are!" The little girl jumped up and down exciteditly.

"You're gonna play with us, right Bill?" Dipper looked up at the floating triangle hopefully.

"Hmm," Bill crossed his arms before uncrossing them and pulling a watch out of…somewhere. "I don't know…I might not have the time."

"Please, please, please!" The twins pleaded in perfect harmony.

"Weeelll…" Bill turned away, as if contemplating some more, before turning to the twins with wide arms. "I guess spending a little time with you two wouldn't be too bad!"

"YAY!" The twins cheered loudly and jumped up and down.

"Quiet!" Lauren's voice screeched through the open door. "I'm on the phone!"

The three of the scowled at the open doorway before turning to each other.

"That's your babysitter? No wonder you don't like her; what a sourpuss!"

Dipper and Mabel giggled at the insult, even though they didn't truly understand the meaning.

"Well, I've got an idea for a fun game," Bill's eye twinkled with mischief, "Let's play: 'Bug The Babysitter!'"

XxXxXxXx

"Again, we are so, so, sorry." Mrs. Pines said as she took paint covered rag from Lauren.

The teenager simply glared towards the kitchen, where the twins and Bill were peaking around the corner and trying not to giggle. A look from their mother put a quick halt to anymore laughter.

Lauren was covered head to toe in paint, feathers, and glitter. The look she was giving the twins was one that spoke of pure hatred.

"I promise, I'll have a good long talk with them so next week, when you come back, they won't ever think of doing something like this."

"You can find someone else." Lauren snapped. "I am never babysitting these hellions again."

Mrs. Pines, who had been pulling a twenty out of her wallet, paused. She seemed a mix angry that Lauren had called her children 'hellions' and horrified at the fact that the young girl would never babysit her children again. The teenager ripped the twenty out of the woman's hand and stormed out; not before casting an evil eye at the twins once more. Mrs. Pines didn't even bother trying to chase the girl and beg her to reconsider; she knew it was useless.

Instead, the mother of two whirled and glared at her children.

"To the bench, now!" She ordered, pointing towards kitchen table's bench.

Mabel and Dipper trudged towards the bench and struggled momentarily to get up on it. Bill decided play along and he sat on the open space of the bench next to Dipper.

"Now I want an explanation." The Pines' mother stood in front of them fiercely with her hands on her hips. "Why in the world would you do that to your babysitter?"

"She was being mean!" Mabel immediately shouted, only to shush herself the moment her mom's glare turned on her. "Well, she was."

"Yeah," Dipper jumped in to defend his sister. "She was totally mean. She would tell us to stay in the playroom and then go talk on the phone for the entire time! She got really mean whenever we asked her to play with us."

"So that's why the phone bill is so high." Mrs. Pines mumbled to herself before sighing. "And does that make it right to cover her in paint and feathers and glitter? Where in the world did you get all these things?!"

"Bill." Mabel and Dipper answered, pointing to Bill.

"Wow, rude." The glowing triangle looked at them with an offended look. "Way to throw me under the bus."

"Sorry Bill…"

The twins' mother looked at them with a look of confusion.

"Bill? Who is Bill?"

The two stared at their mom like she was the stupid one.

"Bill is Bill, silly!" Mabel giggled.

"Bill, this is our mom, mom. Mom, this is Bill." Dipper introduced the two.

Bill tipped his hat.

"Nice to meet you ma'am!"

Dipper and Mabel looked to their mom, but were confused when their mom wasn't even looking at Bill.

"Mom," Dipper whispered loudly, "Bill is sitting right here."

"Oh! Right, of course…Um, It's nice to meet you Bill."

Again their mom was looking at a spot slightly higher than where Bill was sitting. Mabel and Dipper gave each other a look and wondered just what was wrong with their mom.

"So," The mother spoke again, but this time her words were slow as she thought out a way to shape her words. "Bill is your friend? Both of yours?"

"Yep!" Dipper said proudly as his sister nodded along. "It was his idea to prank Lauren though. Sorry Bill."

Bill shrugged. "Its fine kid, it was pretty funny anyway."

"Um, okay. Well, even if it was…Bill's idea, it still wasn't very nice at all! So you two are in for some timeout sessions."

The three trouble makers complained and pouted, but their mom was firm. She put the twins in separate areas, Dipper had to sit on the steps leading to the second floor and Mabel sat in the corner of the living room. The two weren't allowed to be in the same room during time outs because they would find ways to play with another. The twins didn't say anything when Bill wasn't punished because they knew their mom was already acting weird with Bill as it was. Plus, they didn't want to see Bill punished either (even though it was mostly his thought anyway).

"Just wait till your father comes home." Their mother huffed before heading to the kitchen to start on dinner.

Bill hovered around and went between Mabel and Dipper, entertaining them during which had to be the longest timeout in timeout history (when really, it had only been a half hour, but that's a lot for a little kid who can't even tell time yet). Later, once their timeout was over, the two had been told to go stay in their room until their father was home. The two twins turned to their new friend for answers when they finally had a chance to talk.

"Bill, how come mom was acting so weird around you?" Dipper asked.

"Well, it probably has to do with the fact that she can't see me!"

"What!" Mabel went and poked Bill, who giggled and quickly pushed the girl's finger away. "But we can see you!"

"Of course you can see me; you two were the ones who summoned me. Plus, I can make it so only certain people can see me. It's best if your parents or other people don't see me at the moment. People might say some rude things about me, and that's just hurtful."

"Why would anyone say hurtful things about you Bill? You're so cool." Dipper had a confused look.

"Aww," Bill reached down and pinched Dipper's cheek, much to the young boy's dislike. "You're such a cute kid; you're gonna make me blush!"

"What about me!?" Mabel jumped up and down. "I'm cuter then Dipper!"

"Hey!"

Mabel stuck her tongue out at her brother, who stuck his tongue out as well. Bill chortled at the two.

"Oh wow, you two are much more entertaining than I thought you'd be! And yes doll, you're cute too."

"Thank you Bill!" Much faster than Bill had anticipated, Mabel reached forward and with a surprisingly strong grip, hugged the floating triangle and proceeded to place messy baby kisses on him.

"Hey, whoa!" Bill managed to finally wiggle out of Mabel's strong hold. "Whoo, you move much quicker than I thought you would; at least buy me dinner first, ha!"

The floating demon slapped his knee as he laughed at his own joke, not noticing Dipper and Mabel shooting each other conspiring looks. After he finally stopped laughing, Bill floated a bit closer to the twins.

"Well, that was fun. Now what do you two want to do?"

"Well…" The twins looked at each other with growing grins and Bill wondered briefly if he should be alarmed.

'Nah.' He thought to himself. 'They're just little kids; they can't do anything too harmful.'

"Kisses attack!" The twins shouted before suddenly jumping their new friend.

Bill could've done a million and one things to get out of the Pines twins' hold, but he didn't. Instead, he let them do what they want with a sense of amusement. But really, with a cry of 'Kisses attack', he should have been expecting the attack he got.

Just like before, he got messy baby kisses, but this time it was doubled. Bill couldn't help but laugh, even as a part of him thought the excess wetness on him was super gross, because the whole situation was silly. Not because he was ticklish or anything; demons weren't ticklish. Nope. Not at all. But they did get flustered though.

So when Bill finally pulled away, instead of being his normal golden color, the floating triangle was a pale pink color. The demon floated in the air, high enough that the twins couldn't grab him, and took of his hat to fan himself with it.

"Bill, you can change colors?" Dipper gasped in awe.

"Oooh! Turn purple! No, blue! No, turn rainbow with sparkles!" Mabel jumped around, waving her arms wildly.

Bill slowly turned back to his normal yellow color and placed his hat back where it belonged.

"Well, yes, I can change colors. It's mostly just when I feel extreme emotions. Or if I decide to change shape or so."

Bill suddenly started vibrating violently and glowing brightly. The demon stopped before pulling his pocket watch from nowhere and looking at it.

"Welp, would you look at the time? It's time for Bill to go kiddies!"

"No!"

"Don't go!"

"Aww," The demon's eye was wide as he took in the twin's watering eyes. "You two look so cute when you beg! But it's time for me to go! I have things to do and deals to make so I can't stay around and play all day."

Bill ruffled both of the children's hair and even patted the top of their heads a bit when he heard sniffing coming from them.

"Hey now, don't cry! Your favorite friend Bill will come visit as much as I can, okay?"

"That's what James said too." Mabel glared at him through tear filled eyes.

"Don't leave." Whimpered Dipper.

"Hey, tell ya what," The demonic entity pulled away from the twins a bit before squeezing his hands together. He slowly pulled the hands apart and a golden light spun rapidly between them. The more he pulled his hands apart, the bigger the ball grew until it started to expand in size. Right before Mabel and Dipper's amazed eyes, the ball of light shifted and finally rested on the shape of a cat.

A stuffed golden yellow cat with a black bow tie and a single wide eye was held in Bill's hands before he handed it over to the kids.

"Here you go! Now whenever either of you two wanna talk to me, just speak to this handsome little fella and I'll see and hear everything you say."

"So you'll play with us again?" Twin looks of hope shone brightly and Bill chuckled.

"Yep! I might not be able to play all the time, but I'll be watching you too so I'll know when to come."

The twins cheered and reached to hug their new friend and Bill let them before handing them the stuffed Bill cat. The two children held their new stuffed animal between the two of them when Bill pulled out of their grasp.

"Well kids, I'll see you soon! Remember, I'll be watching!"

And then Bill disappeared in a bright light; just like he had appeared.

Mabel and Dipper stood together in their bedroom, blinking the spots out of their eyes and staring at the space their new friend had just been.

"Whoa…"

The two turned to each other before squealing with joy and jumping up and down.

"Bill is so cool!"

"And he can do that-"

"I know! And with the-"

"And when Lauren screamed-"

The two broke into giggles as they jumped up and down in joy.

"KIDS! Come downstairs right now; your father is home and would like a word with you two!" Their mother's voice echoed off the walls from downstairs and the two gave each other a worried look.

"Uh oh…" They spoke in unison.

The two of them set the stuffed cat that Bill had given them on Mabel's bed before slowly making their way downstairs where they knew their parents were waiting.

XxXxXxXx

"I just can't believe that they would do this." Mr. Pines shook his head in disbelief.

"Well they did." Mrs. Pines let out an irritated sigh. "You should have seen Lauren when she walked out of here. She was covered in paint, feathers and glitter-oh, stop your laughing! What if the kids wake up and hear you? They'll think it's okay to pull things like this all the time."

Mr. Pines coughed, hiding the rest of his laughter. By the look his wife was giving him, it wasn't a very good job.

"W-well," He choked back another laugh, "Where in the world did they come across the paint and feathers? Glitter I can understand; Mabel has glitter by the buckets in the playroom."

Mrs. Pines pursed her lips.

"That's the strange thing. They said their friend Bill got it and that it was his idea."

Mr. Pines perked up excitedly.

"Bill? Mabel and Dipper have a new friend? That's great!"

"No, it's not."

"It's not?"

"No, well, maybe, I don't know!" Rubbing her forehead, the woman gave her husband a thankful look when he rubbed her back in a comforting gesture.

"You see, I think Bill is an imaginary friend of theirs. When they introduced me to him, they both stared at the same spot and spoke to him as if he was really there."

"Well, that's nothing too strange." Mr. Pines smiled. "I had an imaginary friend as a child as well. It's just a normal thing kids go through. Once they start school I'm sure they'll make friends of their own and this 'Bill' will go away."

"Maybe." Mrs. Pines sighed and leaned against her husband, who held her dutifully. "Still, we have to find a new babysitter now though."

"Yeah," The man laughed softly, "I guess we do."

The two of them walked down the hallway towards their room but stopped at a cracked open door. The parents pushed the door open slightly to peek inside. Inside, both twins were sleeping in their respective beds. A nightlight spread light throughout the room and along with the hall's light, the parents could see something sitting on the small bedside table that sat between the two siblings beds.

"Is that…a stuffed cat? Did you buy them that?" The Pines wife looked to her husband, who had a confused look on his face.

"No, I didn't. I saw it when I put them to bed, but I thought that maybe you bought it for them."

The mother scoffed.

"After how they reacted today, there is no way I'm buying them any toys anytime soon."

"Hmm…Maybe it's from Uncle Stan? Maybe he sent a package to them and we just didn't see it? You know how the twins are; once we taught them how to spell and read their names they'll open anything that has their name on it. Plus, it looks like something Uncle Stan would send them."

"No arguing with you on that." Mrs. Pines smirked playfully at her husband as the two pulled out of the twins' room, although they made sure to leave a crack. What they didn't notice was the single eye of the doll seemed to shine for a moment before dying back down as quickly as it had started.

The twins in response, smiled and snuggled more into their pillows as their dreamless sleep turned into dreams of playing with their new friend Bill.

Fin

Notes:

True story: I knew a pair of twins when I was really little who would do 'Kisses Attack' on everyone and anyone. Didn't matter if it was a boy, girl, the teacher, or a dog; they did it to everyone. That's where inspiration for that came from.

Also, inspiration for the plush Cat!Bill came from tumblr. There is some really cool art pieces of Cat!Bill and they are adorable/terrifying.

Final: LYN! I hope you enjoyed this! I had a lot of fun writing this and I just loved your prompt to pieces. It grew and grew so it's a lot longer than I expected, but oh well!

Thanks for reading!