As always, I own nothing and Maggie is awesome.
And if Molly seems a bit too old for eight, excuse it away by virtue of being Percy's daughter. :)
Molly
As a little girl, Molly Weasley had gorgeous, long red ringlets that were the envy of every little girl her age.
When she was seven, she cut them off in a fit of spite.
When Molly's mother, shocked, asked why, her response was incensed and immediate: "Because Fred and James said they make me look like a girl!"
And from that time on, Molly's fiery red hair was kept short. At that length, it couldn't curl, though it still wanted to, and so it just stuck up every which way, an image Molly helped along. And once the curls were gone, Molly presented her parents with a list of all the other adornments she wanted removed from her life and wardrobe — ribbons, bows, lace, sparkles, frills, ruffles, dresses, and pink. In short, anything and everything that attributed 'girl' to her in any way.
Molly Weasley was the textbook definition of a tomboy. She hated tea parties, dress-up, and anything related to princesses. She much preferred to spend her time making mud pies, climbing trees, and trying to convince her aunts and uncles to let her try out their broomsticks. She refused to wear shoes from May til September, and every single item of clothing she owned had a grass stain or mud on it somewhere. This was how Molly wanted it, and her parents, though slightly bewildered by the sudden reality that they didn't have the daughter they'd thought they had, let her put away the frilly dresses and be who she wanted to be.
At the age of seven, Molly had believed that getting rid of the curls and dresses would do the trick with James and Fred, but even after her hair had been chopped off and she'd started running around in overalls, her cousins James and Fred were a constant source of frustration for the young girl, and not for the reason why they were a constant source of frustration for everyone else in the family.
Molly was four months younger than James and just one month older than Fred, so by all rights, she should have fallen right in with them. But James and Fred were adamant that they would have nothing whatsoever to do with girls in any capacity.
James and Fred were widely acknowledged to be the trouble-makers in the family (And no wonder, the adults all said amongst themselves, given their namesakes), but Molly saw them for what they were: small time. It was all throwing mud at the girls and dropping Dumgbombs and hiding worms and frogs under pillows – boy stuff, gross, dirty, and entirely lacking in finesse. They did what came into their heads as soon as it did, all noise and mess and nuisance. No subtlety. No creativity. It was almost a crime.
Molly knew that James and Fred's refusal to let her play with them because she was a girl stemmed entirely from the fact that they were boys and therefore inherently stupid, but it didn't make her feel any less lonely.
Finally, the start of the summer that she turned eight, Molly decided to take things into her own hands. Her father always said you could do anything you put your mind to with patience, determination, and a good enough reason, so Molly squared her shoulders, took a deep breath, and approached James and Fred where they sat playing Exploding Snap under a sycamore tree in Grandma Weasley's backyard.
"Can I play?" she asked. The boys looked at her, then at each other, then burst out laughing.
"No," said James, turning back to the game.
"C'mon, why not?" Molly asked.
"Because we don't play with girls," Fred told her, grinning at James. Molly scowled.
"That's a stupid reason," she told them. "I can play Exploding Snap as good as either of you!"
"No, you can't," James said. "You're too busy playing with your tea set and dolls."
"Yeah, and your dress-up," Fred added, and the boys laughed again.
Molly's hands balled into fists at her side. "Just 'cause I'm a girl doesn't mean I can't play cards or fly a broomstick or pull pranks just as good —"
"Yeah, sure, Molly," James said with a grin to Fred, like they were sharing a good joke, like she'd said something funny.
"C'mon, James," Fred said, standing and gathering the cards. "Let's go."
And with a last laugh at her expense, the boys ran off. Molly watched them go, hands still balled into fists, cool hard anger settling down inside her. "Well, I guess we'll see about that," she said to their retreating backs. "Won't we, boys?"
Patience and determination and a good enough reason, that's what her dad always said you needed. She'd always had the patience and the determination, and now the boys had given her the reason.
She started small. Little things here and there, thoughtless things, careless things that everyone assigned to James and Fred automatically, and that James and Fred couldn't refute because they honestly couldn't remember if they'd done them or not. Things like leaving the back door open, tracking mud on the carpet, forgetting to latch the chicken coop.
Then she moved on to slightly more intrusive things - frogs in people's shoes, cookies snitched from the kitchen counter, common items likes keys and quills and once or twice someone's wand moved from one side of a room to the other when no one was looking - deeds that would have been attributed to a poltergeist if the Burrow had had one and if James and Fred hadn't been notorious for such antics.
She did these things carefully and methodically, paying close attention to what James and Fred were doing on their own, listening for the murmurs of the aunts and uncles growing more and more frustrated, timing her actions for when they would cause the most irritation.
And she eavesdropped on the boys, as they planned their "big" pranks of the summer, and she planned ones to match - nothing too clever, nothing too elaborate, nothing close to what she was capable of, but she had to match the boys' reputation. So she balanced buckets of water over partially opened doors and she froze spiders in ice cubes and she rigged the tops of the salt shakers to come off whenever used. The Burrow echoed with frustrated shouts of "James!" and "Fred!" and Molly smiled gleefully to herself each time she heard such a shout.
And meanwhile, James and Fred played, unknowingly, right into her hands by being their usual irritating selves and not paying attention to anything else. Because they just went about their business as usual, and had no idea that the adults thought they were being twice as troublesome as normal.
But the coup de grace came three weeks into the summer. Molly had overheard (by virtue of climbing the massive sycamore tree right outside the boys' window) that James and Fred planned to cause a huge mess in the front of the house as a diversion, then sneak their mothers' racing brooms out of the broomshed and take them for a spin around the orchard.
Now, Molly could see any number of issues with this plan, and knew that the boys would probably manage to get caught all on their own, but there was no harm in ensuring it, and there was no harm in making sure Aunt Ginny and Aunt Angelina were already hopping mad when they discovered their sons sneaking out of the broomshed, top-of-the-line racing brooms in tow.
It was easy - almost insultingly easy. She merely re-rigged their mess to go off three minutes earlier and redirected it toward the far side of the house, so that when the parents followed the trail back to the source, they would come around the back corner just in time to see the boys closing the broomshed door behind them. After that, all Molly had to do was climb to her hidden perch in the sycamore tree and watch it all unfold.
And it unfolded beautifully. Aunt Ginny and Aunt Angelina read the boys the riot act, citing all the mayhem that had been caused by them and by Molly over the past few weeks, and when the boys, in outraged confusion, denied those things they hadn't done, it set their mothers off all over again. Molly lay back against a branch and grinned vindictively.
The riot act ended with James and Fred's broomstick privileges being taken away for two weeks, and they also had to spend the next five days scrubbing the Burrow from top to bottom, starting with the mess they'd made of the front yard.
Immediately, though, they were sent to their room and magically warded against mischief (a handy spell Uncle George was currently in the process of refining and patenting). It didn't stop them from talking in outraged tones about the unfairness of their punishment and who could possibly be behind the things they hadn't done.
Molly knew a cue when she heard one, and when Fred said, "Things like that don't just happen, though! Somebody has to be behind it, and I think somebody's framing us!" and James said, "Okay, but who?," Molly took the opportunity to swing in through their open window.
"Hello, boys," she said with a smile. Their reactions were priceless.
"You!" Fred breathed in an accusatory manner.
"No," James said immediately, refusing to believe it.
"Who else?" Fred asked James, then turned to her and said, "Did you?"
"Who, me?" Molly replied, all innocence. "A girl?"
Fred had the decency to look a little embarrassed, but James's eyes narrowed. "What are you playing at?" he asked, and Molly continued to feign innocence.
"I don't know what you're talking about," she said, pretending to examine her nails for dirt with an air of utter nonchalance.
"Are you the one who's been framing us?" James demanded, and Molly just stared the two of them down.
"How?" Fred asked then, and Molly snorted.
"Please," she said with all the eight-year-old disdain she could muster. "Like it was hard."
James looked downright offended by this statement, but Fred seemed to consider Molly, really consider her, for the first time. James noticed. "Fred," he hissed, "don't you dare."
"What do you want?" Fred asked her.
"I want in," Molly said simply, ready to negotiate.
"No way," James said immediately. "We'll tell. We'll tell them it was you."
"No, you won't," Molly countered. "And even if you did, who'd believe you? All the stuff you've pulled on me?"
"She's right," Fred said to James.
"Fred, don't you dare," James warned. "Stay with me! She can't keep this up all summer. She's got nothing."
"I wonder," Molly said slowly, "just how much trouble you two would have to cause before your parents took away your tickets to the Quidditch World Cup at the end of the summer." She pretended to give the matter serious thought as the color drained from the boys' faces. "This is an interesting thought experiment. I will have to consider it carefully."
"You wouldn't," Fred said. Molly fixed him with a piercing gaze.
"Wouldn't even be a challenge," she said in a pointed voice, all mercy gone.
They stared each other down for a long moment, until finally, Fred nodded. "Okay," was all he said, but Molly knew she had won.
"Fred, no!" James said in shock. "She's a girl!"
"She's not a girl, she's a criminal mastermind," Fred countered with something like fearful respect in his voice. "And I'm not losing my ticket to the Cup." They held a brief and silent conversation, then James, against his will, turned to Molly.
"You'll admit it was you, if we let you in?" he asked. Molly laughed.
"Not likely," she said without hesitation. "But in the future, you'll have me working with you instead of against you. I've done this all summer, and not only not been caught, no one even suspects me. You two might actually amount to something, with me as your friend. Take it or leave it."
James and Fred may have lacked finesse, but they weren't idiots. They knew when they were beat.
And that's how Molly Weasley joined ranks with the boys. Nothing was quite the same after that, and it took the extended Weasley family a while to understand exactly what had hit them. Percy tried to believe for a long time that Molly was just an unwitting accomplice in the boys' schemes, but in his heart, he knew what everyone else soon came to know: Molly Weasley was, in fact, a criminal mastermind.
"After all," George Weasley said to Percy, putting it best, "she's combining the boys' love of mischief with your brain for planning, Perce. I give her fifteen years to achieve world domination, and Merlin help us all when those three get to Hogwarts."
Hogwarts, like the Weasley family, wouldn't know what hit it.
I had a lot of fun writing this Molly, largely because I love giving Percy daughters so completely unlike himself, though Molly is what Percy could have become if the twins had ever been able to corrupt him. She has all her father's intelligence and cunning , and one of the first things I knew about her was that she would fall in with James and Fred, the brains behind the pranks, and Percy would try so hard to believe that she was just following the boys' lead, but he knew his daughter far too well for that to work.
I'm also very interested in who this Molly grows into, and the role she plays in this trio as all of its members grow older, but that is a question and a consideration for later, when these three get their own, longer, spin-off story.