Title: Influences
Author: slacker_d
Crossover: Orphan Black/Pitch Perfect
Pairing/Characters: Cosima/Sarah, Beca/Aubrey
Summary: AU Beca looks up to her older sister Sarah and her girlfriend Cosima, wanting to emulate them both.
Disclaimer: Not mine.
A/N: So this AU crossover exist because of conversations with kiarcheo. Science stuff found online.

"Sarah. Sarah."

Cosima eyes open slowly and she blinks, head still full of sleep.

"Sarah. Sarah."

"Piss off."

"Sarah, wake up."

"Sleeping. Go way."

"But I'm hungry," Beca complains.

"So eat cereal," Sarah mutters. "You do every Saturday."

"We're out," Beca replies.

"Eat something else."

"I can't use the stove yet, 'member? And there's nothing else."

Cosima sits up, groggily and smiles at Beca, who is kneeling by Sarah's head.

"What time is it?" she asks.

"Nine," Beca says.

Sarah groans.

"I'll take you to the store, Bec-a-roo," Cosima offers as she climbs over Sarah.

"Good," Sarah huffs and then rolls away from Beca, into the space Cosima just vacated. "Sleeping."

Cosima grins and kisses Sarah's cheek.

"Cos," Sarah whines.

"Come on Beca," Cosima says. "Well go get some coffee for me and cereal for you."

Beca lets out a loud whoop.

"Beca," Sarah growls.

"Let me get dressed and I'll meet you downstairs," Cosima whispers.

Beca nods and tip toes out.

Cosima quickly pulls on her jeans and throws on one of Sarah's hoodies before slipping out of the room. She can't help but smile at the way Beca is bouncing quietly at the bottom of the stairs. She grabs Sarah's boots and slips them on. "You grab the money?"

"Yep."

"Awesome," Cosima says. She takes Beca's hand and the two of them exit the house. Cosima's not quite awake yet and Beca seems to know this, so she stays quiet—though she is hopping along besides Cosima.

"When'd you get up?" Cosima asks, eventually.

"Six-thirty," Beca answers.

"You were very patient," Cosima says.

"Sarah is really scary if you wake her up too early," Beca replies.

"I know," Cosima agrees.

"Thanks for coming with me," Beca says.

"Hey, we can't have you starving," Cosima replies. "Your mom would never trust me again."

Beca grins back.

Cosima's been dating Sarah for about six months and though Sarah finds her little sister extremely annoying, Cosima finds the eight year old cute. She looks up to her big sister and doesn't seem to mind how grumpy Sarah is towards her.

When Sarah and Beca's grandmother fell and broke her hip, their mom is the only one who could go and be with her. Because it was the middle of the school year, she had no choice, but to leave the girls behind. Since fifteen year old Sarah is less than trustworthy, Cosima had been shocked to learn that she was allowed to stay over and be in charge. The sisters had both been pleased by this, Sarah for obvious reasons and Beca because she knew that Cosima wouldn't just ignore her.

Cosima had been given an envelope full of money that she hid—she kept a bit of it out, knowing that Sarah would start looking for it otherwise. She was given instructions, mostly about what Beca needed and her schedule. It was just understood that the only thing needed for Sarah was to keep her out of trouble and make sure she went to school. And then with a hug for each of them—even Cosima—their mom had left. That had been on Wednesday morning. Sarah had agreed to go to school only because it would reflect badly on Cosima if she didn't—which was a brilliant move from Sarah's mom. And then the two of them had walked Beca to school.

However, today is Saturday and Sarah will not be pulled out of bed before noon. Cosima hadn't been worried since Beca is perfectly capable of getting herself cereal in the morning and then watching TV. Except that they'd forgotten to check how much cereal was left. Beca explains on the walk to the store that there was cereal in the box, but it had only been two handfuls and that there was no bloody way she was eating her mom's shredded wheat.

Cosima smiles at Beca trying to copy her big sister. She knows their mom isn't happy with Beca trying to be a badass like Sarah. Cosima's hoping she can maybe lure Beca towards science. It's no secret that she looks up to Cosima almost as much as she looks up to Sarah.

As an only child, Cosima's always wanted a little sister. Sarah always jokes that she can take Beca, but Cosima might actually take her up on that offer. She totally wants to help Beca with her homework and maybe help her with her first big science project. Cosima's pretty sure if she can make it something fun enough, she can make Beca into a science geek.

When they reach the store, Cosima doesn't go in immediately. Though obviously impatient next to her, Beca stays quiet and waits.

"Instead of cereal, I have a better idea," she says finally.

"What?"

"Why don't we go across the street and get pancakes?" Cosima asks. "We can get some cereal on the way back."

"I don't think I brought enough money," Beca tells her, holding up a ten dollar bill.

Cosima digs through all her pockets and finds a twenty in Sarah's hoodie. She's pretty sure it's the money Sarah won from Paul the other day for doing some stupid dare that Cosima hadn't been paying attention to.

"This should help," she says, showing the bill to Beca.

Beca grins.

Cosima takes the ten from Beca and slips it into her jeans with the twenty. She then takes Beca's hand and they cross the street.

They find a booth in the half full diner and order coffee for Cosima and chocolate milk for Beca before being left alone to look over the menus.

"Mom doesn't let Sarah drink coffee," Beca informs her as Cosima adds a bit of cream.

"Your sister doesn't need the caffeine like I do," Cosima replies.

"Cause she sleeps in so late?" Beca asks.

Cosima reaches out and ruffles Beca's hair—and surprisingly Beca lets her. Cosima knows that she ducks out of the way when Sarah does it. Though that might be because Sarah also calls her cute while doing it—Beca doesn't like being called cute anymore than Sarah does, even though both are totally adorable.

They both order pancakes and the waitress accepts the menus back with a tired smile. Beca sips her chocolate milk out of a bendy straw and kicks her feet. Knowing she would do this, Cosima isn't sitting directly across from her.

"So how's school?" Cosima asks.

"Fine," Beca replies.

"What'd you learn yesterday?"

"Subtracting big numbers," Beca says.

"How big?"

"Like ninety-seven minus fifty-three," Beca explains.

"Do you know the answer?"

"Uh... forty... four," Beca thinks out loud.

Cosima nods. "Awesome. What about science class?"

"Ummm, we learned how to separate salt and pepper with a spoon," Beca tells her.

"Seriously? That sounds awesome. How?"

"Static electricity," Beca says. "Rubbing a plastic spoon with a wool cloth, makes the pepper jump and cling to the spoon."

Cosima grins. "Sounds cool. Do you know why it does that?"

"Uh... cause the spoon... has a negative charge and the pepper is a positive charge," Beca explains. "And positive and negative charges are attracted to each other."

"But isn't the salt positive too?" Cosima asks.

Beca nods. "Yeah, but it, uh, weighs more, so it doesn't move as easy as the pepper."

"Right," Cosima agrees.

Their food appears at this point and Beca is quiet as she pours syrup on her pancakes and carefully cuts it with her fork. Cosima follows suit relishing Beca's happiness. This was such a good idea.

Though Beca is obviously enjoying the pancakes, she keeps sneaking looks at Cosima.

Finally when she's mostly finished, Cosima asks, "Something you want to say, Bec-a-roo?"

"Uh... what did you learn in science?"

Cosima grins. It's already starting. "Periodic law," she says, trying to figure out how to explain it to Beca. She asks their waitress for a pen when she comes to pour more coffee. She quickly sketches out the shape of the periodic table on a napkin. "So have you ever seen this before?"

Beca thinks for a moment and then shrugs.

"It's called the periodic table," Cosima explains. "And it lists elements, like hydrogen, which has an atomic weight of one or oxygen, which has an atomic weight of eight. And they make up water. Two hydrogen and one oxygen." Cosima draws three circles and writes H in two and O in the other.

Beca nods.

"And so the elements are split up by their atomic weight, but also into groups, by the way the table is laid out." Cosima adds more lines. "This table is read left to right, top to bottom, and is usually also separated by colors so you know what kind of material it is. Does that make sense?"

"Kind of," Beca says.

"And then it starts to get more complicated," Cosima finishes. "When you start talking about new theories that have emerged since the table was first created like a hundred and fifty years ago and we've learned a ton more things about science."

"Oh."

"I know it probably doesn't make complete sense to you yet," Cosima says. "But I can't wait to talk to you about it when you get older."

"What if you and Sarah break up?" Beca asks.

"Why would Sarah and I break up?"

Beca shrugs. "Mom says Sarah's... difficult."

Cosima grins. "She has her moments. But I kind of love her, so... Besides, she's the one of the few people I've met who finds me, 'geeking out about science' as she puts it, totally awesome."

"I like it when you talk science," Beca offers.

"Which is why I can't wait to talk science with you when you get older," Cosima says.

"Okay," Beca grins.

"So anything else interesting happening at school?" Cosima asks as Beca finishes her food.

"No," Beca says, eyes on her plate.

"Nothing, huh?"

"Nope," Beca replies, still not looking up.

"Not even something you're embarrassed about?" Cosima tries.

Beca shakes her head.

"Oooh, do you like someone? Don't be shy," Cosima tells her.

"I'm not," Beca insists

"But you like someone?" Cosima continues.

Beca nods.

"What's their name?"

"Aubrey."

Cosima grins. "What's she like?"

Beca doesn't reply.

"C'mon, Bec-a-roo," Cosima tries. "I wanna know."

"She's ten," Beca says finally. "And she's super smart. She reads a lot. And she's kind of bossy, but she's nice to me on the playground."

"An older woman, huh?"

"She probably thinks I'm a baby," Beca grouses. "She's in fourth grade."

"Yeah, that's a pretty big difference," Cosima agrees. "But it won't be when you guys are in high school."

"But that's forever," Beca protests.

"I know," Cosima replies. "Thinking about you in high school is kind of freaky."

Beca nods.

"Can I get you gals anything else?" the waitress asks.

"Just the check please," Cosima answers.

The waitress nods and hands her a receipt. "You can just leave it on the table, unless you need change."

"Thank you," Beca pipes up. "It was very good."

"I'm glad you enjoyed it darling," the waitress grins. "You and your sister have a nice day."

"You too," Beca replies.

The waitress chuckles as she goes to refill someone else's coffee.

"Well aren't you the little charmer," Cosima says.

Beca shrugs. "It's what you say."

Cosima slides out of the booth, puts the twenty under her cup of coffee with the receipt and then pulls Beca into a hug, who eagerly hugs back. Seems like she's more of an influence than she'd thought. But then as she follows Beca out of the diner, she sees hints of Sarah's swagger in the eight year old's walk and chuckles. She wonders when Sarah's going to realize how much Beca looks up to her.

Cosima takes Beca's hand and they cross the street. At the store, they buy two boxes of cereal, more milk, bread and cheese. They both know that Sarah will be starving when she wakes up and grilled cheese is usually what she wants. Cosima's just glad that Beca noticed they were almost out of bread too.

They walk back to the house, Cosima carrying the milk, while Beca insists on carrying everything else. Though a bit bulky, it's not that heavy, so Cosima lets her.

They've only been gone for about an hour, so the house is quiet when they arrive. After putting the food away, Cosima turns to Beca and asks, "Now what?"

"Wanna see the book I found in the library?"

"Sure."

Cosima takes a seat on the couch while Beca quietly runs upstairs to her room. She returns carrying an well worn book and hands it to Cosima.

"Sideways Arithmetic from Wayside School," Cosima reads. "Looks interesting."

"It's brainteasers," Beca explains. "Sarah wouldn't try them with me."

Cosima laughs. "Yeah, that's not really your sister's thing. Why don't you grab some paper and we'll try 'em out?"

When Sarah stumbles downstairs a couple hours later, Beca is carefully working on a graph about how many people will eat Miss Mush's food in relation to how good it tastes, since Cosima's decided it was the easier way to answer the questions.

Sarah slumps onto the couch next to Cosima. "Whatcha guys doing?"

"Brainteasers," Cosima replies, before kissing her briefly.

"Stop trying to turn the kid into a nerd," Sarah retorts.

"Hey it was her idea," Cosima protests.

Sarah sighs.

"What? You think it's hot when I talk science," Cosima says.

"Yeah, but Beca's got badass in her blood or whatever," Sarah replies.

"So why can't she be both?" Cosima questions, thinking of earlier.

"How's this look?" Beca asks, holding up her graph.

Cosima accepts the paper. The two lines crisscrossing across the graph look just like she thought they would. "Looks good to me. You should be able to answer the questions, now, right?"

Beca nods and opens the book back up.

"We got more bread and cheese," Cosima informs Sarah. "Want me to make you make you a grilled cheese?"

"Naw," Sarah replies, standing. "You've been hanging with the brat all morning—"

"Hey."

"...least I can do is make my own food." She leans in for another kiss. "Thanks for getting more bread."

Cosima grins. "Can't have you starving. Your mom would never trust me again."

Sarah just smirks and heads into the kitchen.