There's a WHATquestria?!

"No, really, you're the only pony to ever make Trixie feel shy," Starlight rolled her eyes and popped a fry into her mouth in the most self-content possible way, closing her eyes in bliss. "Damn, these are good."

"Th-they're a big threat to my diet..." Fluttershy mumbled over her tomato salad.

Twilight had not been to Sugarcube Corner since her attempt to "honor" Mrs. Cake.

Between that and her embarrassing confrontation with Trixie, Starlight had called a meeting and furiously demanded that Twilight be accompanied by two friends at all times she was out of the house. She was also to be forbidden from initiating conversations or speaking to "anyone outside the group with bigger wahoogas than me 'n' Rarity" unless forced to.

Pinkie had assured them that Mrs. Cake would eventually convince herself it had never happened, but until then, Pinkie herself had unofficially and temporarily banned Twilight from Sugarcube Corner. To be fair, it was absolutely against restaurant policy to harass the staff, and surely that counted. Of course, anyone else could come in and order for Twilight just fine. Pinkie would never deprive someone of sweets, that was sacrilege.

Still, it was simpler and safer to just head down to HayBurger. None of the staff were stacked, Twilight would not bother any other customers, and no one would bother them unless they wanted to cause trouble. No one wanted to cause trouble with Applejack, Rarity, and Starlight Glimmer.

"I honestly thought..." Twilight wriggled, still very self-conscious about the whole thing, "... that she was way more powerful than me because of... that. That's how it works in Ti -- uh, in my world."

"Are you saying you think Fluttershy can whoop Applejack?" Rainbow Dash raised an eyebrow.

Applejack spat out a laugh, collecting herself. "S-sorry, sugarcube," she offered to Fluttershy.

"It's okay," Fluttershy assured her. "Um, please don't fight me..." she added fearfully.

"W-well, no," Twilight stammered. "Maybe? I don't know how it works for the innate magics. But it works that way for the active magic of unicorns, at least!"

"Ta be fair," Applejack reasoned, "Goin' after Fluttershy means ev'ry bear 'n' gator a good league hence comin' after me..."

"I wanna fight a gator," Rainbow Dash cut in, then shrunk under Fluttershy's shocked glare. "N-not for real! Hypothetically 'n' stuff!"

"Well, darling, our Twilight can absolutely demolish either Trixie or myself," Rarity blushed. "There are a few areas in which I might be able to best her, but none of them are confrontational in nature, and are... largely useless in combat, I'm afraid." She suddenly covered her mouth as though she'd said something she shouldn't.

"Really?" Twilight blinked, beaming. "Are you a particularly talented unicorn, Rarity?" Rarity had never been formally educated, so far as she knew, but she knew the right special talent could turn a self-educated unicorn into a savant. And besides, the more unicorns she could talk to about it, with Starlight and Rarity being the most accessible, the faster she could learn at least the basics of this world's weird, non-titty-based magic - though she was still not sure if it would be profane for her to dare to entertain such exotic powers, or if she was even capable of harnessing them beyond basic levitation and a few largely visual spells.

"Heck yes!" Pinkie chirped. "She was the best in town before Twilight showed up! She can make her whole house do this cute song-and-dance to clean itself up and sort out all her craftin' stuff!"

"Really?!" Twilight gasped.

"Q-quiet you!" Rarity blushed and gently papped Pinkie, who honked like a horn. "It's really nothing special..! There, there are no longterm enchantments, I do a lot of it myself, I just levitate things around and sing to myself a bit..."

"How many focal points can you maintain?" Twilight asked.

"Wha..?"

"Oh, uh, how many things can you levitate at once?" Twilight reworded. The terminology might be different between Equestrias, and Rarity might not have been told them in these words anyway.

"Erm," Rarity fidgeted. "Mm, a dozen or so?"

"What! That's amazing," Twilight blinked, then put a hoof to her mouth, thinking. "Gosh, has my Rarity been hiding this kind of skill from me too?"

"Oh dear!" Rarity blanched. "I, I wouldn't want to reveal her secrets if so --"

"Aw, c'mon, Rarity, bein' good ain't nothin' to be ashamed of," Applejack smiled.

"Well, it's just..." Rarity sighed. "Very well, I'll come clean." She looked down like she'd been caught raiding a pantry.

"Clean..?" Twilight blinked, pausing through a bite of her burger.

"I don't want my Twilight to look at my magic," Rarity rasped with apologetic eyes like she'd just revealed she was cheating on her spouse. "She means well, she would mean no harm, but she... well, you, you're a Canterlot graduate, personally trained by the finest mage alive, I..." Her eyes watered as she ran her hooves over each other and then closed her eyes. "I don't want her to tell me I'm doing everything wrong..."

The girls nodded in understanding. Twilight froze, taken aback. "... Y-you think I'd do that..?" she blinked. This wasn't even her Rarity and she felt kind of... really, really hurt and at the same time, really, really guilty. Their Twilight must have done something to make Rarity distrust her in this way, and something inside her warned that she'd done the same thing to her own Rarity.

"I think she'd do that," Rarity nodded, tears running down her face, "Which is an awful thing to feel about a good friend, but I'm sure your Rarity must have the same worries, and I can see I've dearly offended you by all this a-and that just proves to me that she would be devastated as well, a-and I shudder to think I may have betrayed my other self, even were you to approach her with the utmost grace, she might panic, I'm so, so very sorry..." she sniffed and covered her face.

Twilight smiled. "I understand," she soothed. "I'm sorry for nosing in and upsetting you. I promise I'll be good to my Rarity when I get back home, and I'm sure your Twilight will be kind to you if she knows you're anxious. But you know, it's funny."

"W-what's funny?" Rarity peeked out over anxious eyes.

"I can barely do a lick of magic in this body," Twilight explained. "Even talking with Starlight, I've got pretty much no idea how your magic works. There are some common bases, I can levitate stuff and I can shoot some harmless lights around, but everything beyond that is still not cooperating with me. So you'd be the expert out of the two of us, at least until I can wrap my head around it."

"That is funny," Rarity agreed, smiling.

"And another thing," Twilight pondered. "The fashion here must be different too, right?"

"It changes every week, I swear," Rarity shook her head. "Why did I have to have such a stressful calling in life? I could have been an actress or an engineer."

"An engineer?!" Applejack guffawed.

"Can I come over to the Boutique after we're done here?" Twilight requested. "I'd love to learn more about your sensibilities and maybe see some of your spells."

"Oh yeah," Starlight rolled her eyes, "The fashion's gotta be different where you come from."

The girls stared at her in mixtures of confusion and disapproval.

"Don't give me that look, you know it's true," Starlight shrugged, inelegantly snarfing the rest of her burger.

In Rarity's room, Twilight looked back in forth in wonder at the elegance of Rarity's magic despite the fact Rarity was on the other side of the room, facing away, contentedly feeding cloth through a sewing machine.

"Wow, how do you do that?" Twilight lived up to her name, her eyes sparkling in filly-ish wonder.

"D-do what?" Rarity grimaced, expertly stitching another bit of cloth as her magic assembled previous strips onto a mannequine.

"You're not even looking! You're working just by feel," Twilight examined. "That's amazing. Hey wait, what about the udders?"

Rarity froze, magic and all. "W... What?" She slowly turned to blink at her.

Twilight froze as well. "Um... don't you need something for the udders..?" she grimaced and shrank an inch or two. Oh darnit, I've put my boobs in my mouth again, she fretted. "At least to hold them in place?"

"Actually," Rarity thought that over, her magic resuming as though coming gradually out of a time-stop. However, at the sewing machine she was still facing Twilight, her eyes darting around in thought. "Restraints might help to minimize their presence and avoid unpleasant wardrobe malfunctions..." She frowned. "Mm, but no one's developed a standard to measure that area of the body, female clients would be rather reluctant to say the least..."

"We have!" Twilight perked. "I may not be a seamstress but I've had my measurements taken countless times, I know how to do it! It's pretty simple, even!"

"Really?!" Rarity blinked. "W-well..." She blushed. "Fine. Do it on me. You know where the tape measures are, yes?"

"You'll need to stand up and take a slightly longer stance than normal, like you're crossing a big gap," Twilight told her, examining the tape measure. "Ah, good, we seem to use the same units." She paused. "Isn't that weird? This alternate world thing is really uncanny, isn't it?"

She looked at Rarity, who cleared her throat and avoided her gaze with a blush, because she had her back and front legs a bit further out than normal and her tits were hanging candidly out for measurement. "Yes," she answered, "It is a bit surreal to think there's another world that is so similar to ours, yet so different in this one, very important way."

"I wonder how many other Tittyquestrias there are..." Twilight pondered. She floated the tape over and wrapped it around Rarity's body, over her tail on top, between her udders and legs on the bottom.

She jumped slightly as the tape brushed her knockers. "Er," Rarity considered, "Don't you need to measure my..?"

"It is impossible to directly measure only titty," Twilight explained with authority, "They're quite malleable and where they start and end is ambiguous. So we use a trick to approximate it. We measure the closest spot on your body without titty, and the fullest spot on your body with titty, and subtract. That should be pretty close to your titty size."

"Please stop saying that word," Rarity requested as Twilight wrote down the number and gently removed the tape.

"Besides," Twilight added, "We need two measurements anyway, one for the straps and one for the cups."

Rarity hissed as the cold plastic now wrapped around and slightly lifted her teats. "Oh dear, Fluttershy would hate this," she fretted.

"Unicorns can easily measure this themselves at home, but earth ponies and pegasians have to bite the bolt, yeah..." Twilight sympathized. "I'm gonna hold this here and I just need you to breathe comfortably a few times," she instructed. "Let me know when it feels comfortable - not too tight or too loose. It should feel like it's holding your boobs in place without smashing them against your gut. Well, as well as a tape measure can, anyway."

"Mm," Rarity nodded, breathing in and out slowly. After a few times, she swallowed. "Um, that feels about right..? I mean, it's the first time I've done it..."

"I'm sure you'll revise it over time," Twilight nodded, writing down the number. "And there you go. A bra is basically a band and some cups that hold up your boobs like a hanging fruit basket."

Rarity looked at the numbers and blushed again. "Th-they're a bit larger than I thought," she admitted.

"They're beautiful, Rarity, don't worry. And trust me, our Rarity's big number is like, twice that."

Twilight returned home close to sundown. "Spike?" she called.

"Y-yeah?" Spike answered nervously, peeking at her around the frame of an open door.

"Rarity gave me some good advice," Twilight announced. "Could you take a letter for me please?"

Spike quickly produced a paper and quill. "A letter? To who? You sure this is a good idea?"

"It'll be fine, Spike," she assured him, then cleared her throat. "To Her Most Bounteous Grace, Princess Celestia..."

"Oh loons," Spike grimaced. "I hope they don't shoot the messenger." He began writing, deciding to subtly alter the letter should Twilight say anything too objectionable.