Paste I.
Filomena had gotten the idea from Filius when he started teaching at Hogwarts. Her brother had wanted a way to quickly determine how similar multiple essays were, to be able to tell if students were copying each other's work. Filomena's mind immediately started whirring. (The Flitwick twins were both Charms prodigies, but while Filius focused on performing complex magic for his dueling tournaments, Filomena focused on developing new spells.)
Of course, anyone could tell if the essays had identical wording. The challenge was magically determining the similarity of non-identical essays. Filomena's first hurdle was to highlight all the phrases that were the exact same on two parchments. Her second hurdle was to apply the highlighting spell pairwise to all the parchments in a stack, physically grouping together the pairs with lots of the same phrases. Although this approach required the subjective judgment of the caster to decide how much in common was too much and didn't address the issue of paraphrasing, Filius was thrilled, and Filomena later heard that it became standard practice for professors' grading at Hogwarts.
Distracted by other projects, it was many years before Filomena stumbled across her earlier work and again became interested in the problem. But now, she thought beyond comparing essays that happened to be in the same room. What if there was a way to determine how similar a text was to any other ?
...
Two years later, Filomena had a working prototype. She could detect the most similar texts in the same language that weren't hidden by powerful magical wards, within an approximately 10-kilometer radius. Combining this with some cartography spells she'd picked up from a friend, she could plot an array of dots on a map of the area she was in, colored by the similarity to the text at hand. Filomena didn't know exactly how this spell might be used, but she enjoyed tinkering with it. Her eventual discovery occurred almost by accident.
Filomena was in her friend Cynthia's upscale apartment off of Diagon Alley, sipping chardonnay and swapping stories with her favorite gang of seventy-year-old witches. At one point, she mentioned her new hobby-spell, and her friends wanted to test it out. After seeing an unsurprising scatter of Hogwarts, A History texts / excerpts / derivatives spread around the map of wizarding London, the group conversation moved on. However, after they'd all gotten a bit more tipsy, Cynthia suddenly exclaimed, "Aha!" as she was coming back from the loo, and returned to the living room brandishing a book, her hands covering the title.
"Try this one, 'Mena!" She giggled, placing it on the coffee table face-down.
Filomena shrugged and tapped the book with her wand. The map in the middle of the room instantly lit up with dots. Unlike for other texts she'd tested, the dots seemed to be in just two major hues. Dots in the darkest color, signifying perfect or near-perfect matches, clustered in wizarding London. But dots in a lighter color spread far into …Muggle London? Cynthia flipped over the book with a flourish and a wild grin, and they all saw the title and moving images on the cover.
"50 Shades of Grey?!"
...
This discovery sparked a chain of others. Many, many others.
In retrospect, Filomena had to hand it to the witches and wizards who'd figured out that while they couldn't easily plagiarize mainstream Muggle literature (probably because Muggleborns, halfbloods, or others who frequented the Muggle world would notice and call them out on it), there apparently weren't enough people who (a) read erotic fiction from both the magical and Muggle worlds, (b) were comfortable publicizing this pastime, and/or (c) who cared that there were near-identical books published under different names, for the game to be up. (Typically, there were just a handful of tweaks made in the background of each story, e.g. traveling by apparition or floo instead of car.)
Another surprise was that there was apparently no legal enforcement of Muggle copyright in magical Britain - just the perception of bad publicity if you were caught selling Muggle wares. Filomena and her friends were left to wonder how many other mages were making money off of the creativity of Muggles.
Paste II.
When you hate the person you are (or might become), you have two choices: try to change, or self-destruct. The thing is, in some situations, these two paths might be one and the same.
As a child, he'd had his rebellious moments. He intentionally pressed his parents' buttons, and was punished for it. But his family wasn't especially concerned until he was Sorted into Gryffindor. He never let anyone know how hard he'd had to beg the Sorting Hat for this result.
Sirius wanted to be brave. He wanted to be a good person. But in his heart of hearts, he feared neither was true. While he didn't want to be like his family, he suspected that there were parts of them he'd never be able to fully rid himself of. He was proud, but also intensely insecure about what others thought about him. He desperately wanted friends and others who loved him, but was also entertained by playing with people's emotions and eventually grinding them under his heel. He didn't know what to do with the spite he knew lurked somewhere in his heart.
Sirius' windfall came in the form of James Potter. Brave and caring (even if his arrogance sometimes got in the way of showing the latter), he was a mirror for who Sirius could be. Of course, Sirius was never going to be a lackey like Peter. He made his observations of James, but then breathed his own energy into what he saw. He laughed more, risked countless pranks, and stood up for the non-purebloods in the faces of the prejudiced Slytherins. At home, he upped his rebellion, sticking posters of Muggle girls and motorcycles all over his bedroom. Consequences be damned, he was going to show his family that he was nothing like them. Living this way felt like wearing a Gryffindor costume, and Sirius loved it.
Over the years, there were stretches of time when it didn't feel like a costume anymore. Sirius had found some friends he truly cared about and had numbed his instinct to run from danger. But when he looked closely, he knew there were still cracks. He drowned out his insecurity by turning up the volume of his actions, which had the added benefit of showing everyone else how Gryffindor he was. He ignored the fact that even James was sometimes put off by Sirius' insatiable hunger for daring stunts, dramatic displays of affection for his friends, and aggression towards the Slytherins.
Put on a brave face, so they don't know how scared you are. Exude warmth, so they can't detect the cold within.
Paste III.
Jean Granger perched nervously, uncrossing her legs for the fourth time. Her husband Matthew sat next to her on the couch in their living room, positioned comfortably but drumming his fingers on his leg.
"Do you think we should bring some Pepto-Bismol? The Professor said first-time apparition isn't easy on the stomach."
"Not a bad idea…" Matthew started to say, but Jean was already on her way to the medicine cabinet.
As she came back into the room, she paused and asked, "Should I put on heels? We don't want to embarrass Hermione by dressing too casually."
"You look great, love. Plus, Hermione's mentioned all of the staircases to get to her classes - you'll want to be able to walk up and down those without twisting an ankle."
"Ah yes, you're right." She sat back down, tucking the Pepto-Bismol into her bag and chuckling softly. "My brain's going a bit haywire."
"Lucky you don't sweat as much as I do when I'm nervous," Matthew patted his forehead with a kerchief and grinned ruefully. "I'm thinking how crazy it was that we sent our little girl off to this place two and a half years ago -"
" - And that we let her go back after being put in the hospital wing last year," Jean massaged her shoulder.
"That too. She's got the mind of a lawyer, making such a convincing case that we should let her continue going to Hogwarts." Matthew laughed. "Other parents have to deal with their teenagers wearing inappropriate clothing and sneaking off to parties, but we have to argue with a magical genius who desperately wants to go to school."
Jean sighed, but her mouth twitched with a smile. "I'm just so glad this year seems to be going well -"
She was interrupted by a polite knock on the front door, and immediately leapt up to answer it. On the Grangers' doorstep was a middle-aged woman in plain black robes. Her warm brown eyes were set into a round face with strong features.
"Good morning! You must be Jean?"
"Hello, yes, please come in."
Matthew also stood and greeted the Professor, shaking her hand.
"Please, call me Charity."
...
Their trip to the castle was relatively uneventful: side-along-apparition did make the Grangers' heads spin a bit, but Charity was clearly practiced in traveling with new passengers, so the Pepto-Bismol ended up staying in Jean's purse. On the short stretch of road leading up to the gates, they were met by a silver streak which materialized into what looked like a large, graceful bird made of shimmering smoke. The crisp November air immediately felt mild, and Charity explained, "This is Professor Dumbledore's entourage. He's currently in a meeting with Ministry officials, so he won't be able to greet you in person."
Jean noticed a slight chill again as they passed through the gates, but it quickly went away.
To get across the grounds, they rode in a small, plain carriage that appeared to be moving forward without anything pulling it. The silver bird hovered next to them the whole way, on the side so as to not obstruct their growing view of the elegant but sturdy castle.
After clambering out of the carriage, Matthew helped Jean down and kept holding her hand as they followed Charity up the steps and through the front doors of the school to which they had entrusted their daughter's future.
...
Having recovered their breath after walking up what seemed like a dozen staircases ("It's how I balance out my addiction to Hogwarts' amazing desserts!" Charity laughed), Jean and Matthew walked cautiously into the classroom. They were met by a dazzling, big-toothed smile in the front row. Hermione got up quickly (but carefully to avoid disturbing her pristinely-organized desk) and speed-walked over to give them both hugs.
"I can't believe you're here!"
"We checked this with you a month ago," Matthew joked.
Hermione drew back and sent him a mock-glare, mouth twitching at the sides like Jean's always did. "You know what I mean."
Enjoying her daughter's presence, it took Jean a minute to notice the dark circles under her eyes. She resolved to remind Hermione to sleep more.
Meanwhile, Charity waved her wand and "Guest Speakers: Dentists Jean and Matthew Granger" appeared on the black board in large, neat letters. She then conjured a table at the front of the classroom, and a couple of glasses of water for herself and the Grangers.
As the start of class drew nearer, Hermione helped her parents arrange some of the items they'd brought on the display table. As students started trickling into the classroom, she resumed her seat. Matthew noticed red, yellow, and blue ties, which he inferred represented three different houses at the school. What had Hermione called the houses other than Gryffindor? Slithering, Ravenclaw, and Puffle-something?
Once all the students were seated (there were about twenty), Charity stepped forward and said, "Good morning, everyone! Today we have some very special guests, here to teach you about the field of dentistry. Please listen carefully and think of questions you want to ask. Mr. and Mrs. Granger, the floor is yours!"
Matthew cleared his throat. "Thank you Professor Burbage for inviting us! We thought we'd start with a game. Who can tell me what this is and what it's used for?" He picked up a toothbrush. A few students raised their hands, and Matthew pointed at a girl with a blue tie.
"A teeth-brush? Used for cleaning off your teeth."
"Very good! It's actually called a 'toothbrush'. Now, who can tell me the magical way to clean your teeth?"
More students raised their hands, and Matthew gestured to an androgynous student with a yellow tie.
"Mostly we use the spell 'Alblica'."
"Great. How about this?" He held up a tube of toothpaste.
No one raised a hand. Hermione looked around, brow creased.
Matthew waited a moment more, then said cheerfully, "Looks like we'll have things to teach you after all! This is called toothpaste. It's like minty soap that you put on the toothbrush to help clean off your teeth and keep them healthy with ingredients like fluoride…" He trailed off. "How do wizards get fluoride?"
Again, the room was still. Hermione frowned, thinking.
"Maybe they call it something different?" Jean hypothesized. "Fluoride is a mineral that is very important in preventing tooth decay. Or perhaps there's a potion that fulfills the same function?"
"Yeah, but it's nasty! Dentidraught tastes awful and makes your breath smell." A boy with a red tie piped up.
"Remember to raise your hand, Sam." Charity spoke up, continuing with a thoughtful expression on her face. "But he is correct, many witches and wizards avoid Dentidraught until they start having problems with their teeth, which can be quite painful…"
"Indeed. Cavities are never fun." Matthew nodded, and then looked at Jean. "Want to describe the procedure?"
Over the next 40 minutes, the Grangers shared about their daily work, miscellaneous tools like X-rays, and their rigorous training in dental school. During the Q&A, students asked questions ranging from what uniforms dentists wore, to what their most challenging case was, to whether they had ever been bitten ("And it's not just the kids who bite," Matthew joked).
As the rest of the students were filing out of the classroom, Hermione lagged behind to give each of her parents another hug. Three other students also hung back and approached the Grangers at the front of the room: a boy and two girls with blue ties.
"Thank you for your presentation." One of the girls said shyly.
"You're very welcome. What can we do for you?" Jean asked kindly.
The boy cocked his head. "How expensive is toothpaste?"
...
Harry flopped down on a couch in the common room. "Wood's trying to kill us."
"You did sign up for this," the couch's bushy-haired other occupant replied dryly, eyes still on her book.
"Yeah, yeah." Harry exhaled slowly, then inhaled sharply. "Oh hey! Guess what I overheard in the locker room as I was going in to get changed?"
"Do you think I actually want to know this?" Hermione turned and raised her eyebrows at him, and Harry turned slightly pink after a second of processing.
"Nothing bad! The Slytherin team was leaving, and I overheard one of them telling the other one about this great new thing called 'toothpaste' that was way better than Dentidraught because you could avoid having your teeth rot and snog without bad breath. But the crazy thing was: they mentioned you could buy a vial of it from people at the Ravenclaw table for 5 Galleons!"
Hermione frowned. "That's got to be like eight or nine times the price of a tube in a Muggle store! Also, a vial?"
...
After cornering the Ravenclaws in her class and demanding an explanation, Hermione felt unsure whether to protest their assertion that Slytherins wouldn't buy toothpaste if they knew it was a Muggle product. On the one hand, they were promoting good dental hygiene, which Hermione had been brought up to prioritize. On the other hand, they were throwing away an opportunity to confront blood prejudice, even going so far as to obscure their partnership with several Muggleborn housemates who were managing the toothpaste supply chain.
Eventually, the Ravenclaws bought Hermione's silence with an oath that they would donate 20% of their profits to an organization promoting Muggleborn representation in the Ministry.