There's a WHATquestria?!

Twilight dutifully bowed, then yelped and jumped.

"Cold floor, isn't it," Celestia sympathized with a smile. Indeed, while she had been smacking her tits on every possible surface in Titty Twilight's castle, Twilight had never felt such a horrible and startling sensation in her life. Titty Twilight must have somehow kept her floors warm specifically to avoid such a thing.

Twilight took the opportunity to examine Celestia's peerless undercarriage. Supremely massive, incredibly full, and with large, perky nipples, the heavenly hangers almost obscured her view of the Princess's face, even so far down her body as they began. Well, at least that's the same, she grumbled to herself, dreading the inevitability that she would need to explain to her own Celestia that she was indistinct from her Tittyquestrian counterpart. What was different was that, in addition to Celestia's far more comfortable and exposing posture, Luna had a very similar pair, as she had seen just the other night. Twilight projected that, were they the same height - as they might have been when Luna was "Nightmare Boob" - their udders would probably be near-identical in all but color. Luna was, of course, quite confident in their display to say the least, if not outright competing with her sister in Hark, avast mine tits!

"Twilight Sparkle," Luna droned. "A few nights ago, you and I performed in the Night of the Dancing Pumpkins."

"We did, Your Grace," Twilight nodded.

"At the time, I admit I found your performance to be bizarrely lacking," Luna pouted, "But we have now heard tell that you are not of this world."

"That is correct, Your Graces," Twilight blushed, screwing up her face and trying very hard not to stare at their tits.

"In that context, your improvisation was impressive," Luna praised. "But I must presume from your difficulty then and your bashful gaze now," Luna considered, one hoof to her chin, "... that we are not so royally-endowed in your world as our own."

"Luna," Celestia gently chided, "We should not lord our undercarriages over the people any more than our height, our education, or any other fortunate circumstances of ours."

Are you kidding, Twilight internally rasped. If anyone mentioned my sweet teacher-god-mom's boobs she'd cry, and Luna'd tackle and physically beat up whatever poor bastard humiliated her.

"Of course, dear sister," Luna apologized, "But it is clear that she is disquieted by the magic of boobship, even among the female guards."

One might think Twilight would have a reaction to boobship, but no, she'd heard that phrase and many of its milk - er, ilk - over the course of the past few days.

"That is true," Celestia admitted, nodding with concerned eyes. "Twilight -- " she paused and covered her mouth. "Oh dear, I should not presume. Are you as close to your Celestia as my Twilight is with me?"

Twilight leaned back and wrinkled her nose. "... Define close, please."

Celestia and Luna glanced at one another. "Whatever do you mean?" Celestia fretted. "Is there... hostility?"

"It is my understanding that the Twilight of this world defeated Starlight Glimmer through a form of sexual domination," Twilight said with her eyes closed and her face red. "If that is how she treats her enemies, I shouldn't presume how she treats her friends and loved ones..."

"That is wise," Celestia laughed with a blush. "No, Twilight, we do not have that kind of relationship, and your counterpart's... subjugation... of Starlight Glimmer was an isolated incident."

"She was, however, caught up in the Haremization of Canterlot," Luna added with a pout.

"The what."

"Stupid sexy changelings..." Luna added, her hips squirming.

"Luna, that is besides the point," Celestia tutted, and shook her head. "Do not worry about it, dear Twilight. I can see that you are from a very different world than ours, and my heart goes out to you. Surely, you have come here to seek help in returning to your own world, and perhaps in returning our Twilight to ours. Is this correct?"

"That'd be great," Twilight sobbed with her sore, frozen-cold tits. "Your Twilight must be completely out of her depth, if she talks about boobs half as much as any of the rest of you she must have mortified our most voluptuous residents and... and I can't work under these conditioooons..!" she whined. Or with these conditions under her, for that matter.

"You have our permission to search the royal library," Celestia nodded, "... including the restricted section, though I must warn you --"

"You-have-a-restricted-section?" Twilight suddenly leapt back up and chirped brightly. Of course they would, she thought feverishly. Every library has a restricted section. She frowned, her mouth twitching. Every library. Then she smiled again. I should probably not be smiling at these prospects.

"-- I must warn you that, if what you have experienced so far in this world is at the limit of your tolerance, the candid obscenity of that library may break you," Celestia spoke gently.

"'tis a high price to pay for the off-chance it may aid thee in returning home," Luna judged.

Forbiiiiidden booooob-knooowleeeedge, her mind coaxed her. I mean - best shot hoooome.

"I understand, Your Majesties," Twilight bowed again, keeping her back arched and her tits off the floor. "I'll be careful. Thank you."

"Then go and be well," Celestia gestured with a wing, and Twilight headed off.

The princesses considered for a few seconds.

"Her tits could explode," Luna pointed out, curling up to cradle her boobs uncomfortably.

"Oh come now, Luna, you and I know better than anyone that doesn't happen," Celestia admonished, then furrowed her brows, her wings lowering to cup her undercarriage. "... but it is horribly unpleasant, and we ought to send someone to keep an eye on her."

"What about her?" Luna suggested cryptically. "She would be unaffected by anything in the library."

"Her? ... Oh! Her! Hmm," Celestia considered. "She has been on very good behavior... But we do not know her nature in the other world, this exotic Twilight may take her as a threat..."

"It will be fine, dear sister. I doubt they will attack one another on sight, or anything. Besides, we've no other suitable agents."

"Very well..."

Knowing that the restricted section was both horribly dangerous and horribly fun, Twilight elected to save it for last, rapidly - but respectfully! - rifling through every book she could reach. As she physically tossed each aside, her magic automatically caught them, smoothed their pages, and returned them to their proper places. Had she consciously noticed this, Twilight might have been fascinated that this most base aspect of her and Titty Twilight's magic remained fully compatible, while their profound spells were wildly different. But alas, if Twilight were to warm to the charms of titty magic, it would be after she found a way to get herself back home and these big ol' things off her belly.

Twilight hissed, having attempted to step over a pile of somethings and smacked her enormous boobs, for the fifth time in the same library. She paused to wallow in her pain. "I should ask Fluttershy about those bras of hers," she concluded.

She inhaled, sighed slowly, and turned to the fireplace. "It's always the fireplace," she conjectured. Feeling in with her magic - ew, it made her horn feel slimy - she found a button and pressed it, causing the fireplace's back wall to open.

She leaned down - eeeYYiiIiYyyIiIi! Cold! - and looked into the fireplace. There's no way a fat princess and her fat tits could fit in there, that's for sure. Heck, she wasn't even sure she could get through there. Her body writhing from soreness and cold, she managed to slowly wriggle through, hissing in pain and discomfort, before rising.

She immediately noticed a shaft of light to her left, down a hallway, coming down from the belvedere of a high tower. It shone down upon a glass case, under which was a very suspect black choker with a blood-red cowbell. She should stay away from that thing.

It was otherwise quite dark. She was worried these old parchments may be damaged if she turned up the light, but she wouldn't be able to read them if she didn't, so she put her horn on a very low light-level and began to cautiously look around the library, her eyes pausing again on the necklace.

As she expected, almost all of the artifacts discussed within were mammary-themed. "What is all this awful stuff," Twilight shuddered. Many were written in a language she didn't know, or encoded in some obscure rune cypher.

One scroll showed a series of three mares. One resembling a mare like Twilight with a graduate cap and a petite undercarriage, another showing a mare similar in appearance to Rarity with a coquettish look and a moderate size, and one showing who may have been Fleur de Lis with a drunken expression and four enormous udders dragging on the floor. If Twilight had to guess, it was some kind of brains-to-boobs spell. Four..?! she questioned in her head.

Another showed a sequence of two mares, one of them apparently stealing the boobs of the other to increase her own size, chanting some eldritch evocation. Twilight could take a guess what the catch was, as the caprine demon floating behind the witch easily dwarfed her in stature and in endowment. FOUR?! she mentally cried again.

A final scroll showed a mare who gradually grew horns. Her undercarriage became progressively larger and her face grew more pained, until one image depicted her body blasting off like a rocket, her udders replaced with a cartoonish bomb explosion. Twilight felt a bit ill and closed it at once. Not four, she dimly accepted.

I'm probably only going to find gross things in the rest of this room, Twilight urped, and glanced over the room once more.

Her eyes fell on the necklace again. Gosh, the bell sure was a lovely ruby-steel color. Looking at it made her boobs feel funny. And her cooch. She shook her head and began going through the books on the far wall.

"The Dark Side of Boobship", she read. "Some mares seek to corrupt boobs for the sake of power and are made malafest, twisted in boob and mind." Well, that much is the same as friendship, anyway. Uh, except the boobs part... She glossed through the book quickly. Uzzauzzauzza... "For the boob is a beautiful thing, but the lust of it is a rickety bridge over the pit of wickedness"...

She paused with a start, her face turning red. I... Am I fondling myself? She realized her magic was massaging her udders. Oh my lest, I'm fondling the other Twilight's boobs. She looked both ways, confirming she was alone in the library. ... it does feel reeeaaaally good, though, they're so darn sore..~

She stopped at once and snapped that book shut, blushing deeply. What am I doing!! she thought. Th-they could probably use a rub-down but this is ridiculous! She swallowed, looking all around. W-well, no one's going to see... N-no! Absolutely not!

Her eyes landed on the necklace again. Its sleek obsidian ring, its pristine bell. Gosh, that's a pretty necklace, she thought to herself. Beautiful... something whispered back to her.

She moved closer to the hallway, glancing at the belled necklace now and again as she continued to look through books and parchments. She gasped in scandal, realizing she was reading a manual on how to finely manipulate the breasts of mares, griffons, and even dragons. Supposedly, by stroking, striking, or firing magic onto or into specific regions, they could be soothed, stimulated, dealt incredible pain with little damage, or turned to ash with barely any effort. Twilight wasn't certain if the book was accurate, but the fact that any creature might take the time to ponder such things in such depth was horrifying to her.

Breasts are nothing to be ashamed of, something whispered to her. Of course not, she answered. It's just... this level of fascination with them, this obsession is bizarre...

She was standing halfway down the hallway now, still reading scrolls. The udders of "cowlicorns" are more productive and more sensitive even at the same size, and the sex energy of their orgasms is a potent magical source, she noted. I really did not need to know that! Nice!

Aren't you fascinated? the something asked. Only a few days ago, you were bereft. You've been keenly aware of their presence since you came here. Why not indulge?

Twilight turned and jumped with a frightened gasp. When did she get this close to the necklace? She could reach out and touch the case! She backed away hastily. Her magic began massaging her boobs again, causing one of her back legs to raise and start trembling. ... a-aah, that feels so good..! she admitted bashfully. Her eyes rolled back and she began to pant, her marehood starting to twitch, wink, and drool.

Wouldn't it feel even better if they were bigger? Heftier? More sensitive, the necklace cooed to her. Big enough to smother a yak. Feel them bouncing and jiggling as you rub the perky nipples. Why not give it a try? Don't you want to hear the sound of the bells..?

Twilight paused, panting and sighing, anxious and ashamed, her heart pounding in her ears and lady areas. Even bigger? she considered. They, they already nearly touch the floor... But she was already walking towards it, her thighs wet. And I do want to hear how it sounds...

Twilight's magic let go of her boobs and reached out to feel at the dome, preparing to lift it.

She had only an instant to hear the sound of rushing wind before --

WHAM.

Twilight's mind broke as she collapsed to the floor. "OOUURRRGHHH..!!" Twilight cried and began sobbing again, cradling her tits in her wings. Despite being otherwise unable to think, the custodian of Twilight's mind - herself in an Italian suit and monocle - stoically, neatly dusted today off and, with it, replaced the previous occupant of the file cabinet in her head labeled WORST DAY OF MY LIFE.

"You dumb bimbo!" Whoever hit her began scolding her with an obnoxiously cute, albeit angry, voice. "Don't you recognize the Cowlicorn Carcanet when you see it, Princess?!" Little angry wing flaps informed her that whoever hit her was not very large and was now flittering over her. "Or is it true the bigger the boobs the smaller the brain?! Must be why us foals are the only smart ponies around this dump!" The little someone seized her by two hooves and, lifting her by said hooves so that her tits were not scraping on the floor, began to drag her away from the necklace. This was very slow and inefficient given the drastic difference in their body weights.

"W-wha..?" Twilight sniffled, blinking the flashing lights and tears out of her eyes, looking up at her captor. Her eyes widened. "Cozy Glow..?!"

"Aww -- ya do wemember -- widdle owe me," Cozy Glow huffed while dragging her. It was her, alright, just as Twilight remembered her. How did she escape? How did she make it all the way to..?

"W-what'd you do to your hair..?" Twilight chose to voice first. Cozy's mane, while still fluffy and curly, was swept to one side, like Pinkie when she was sad. A perfect, cute little schoolfilly... As if.

"What're you talkin' about?" Cozy grunted, having finally dragged her back down the hallway. "Get up! Now that you almost got your boobs exploded once, it can't get you as easy."

"A-a-a-almost got what?" Twilight stammered in shock, clumsily rising. "What, what happened?"

Cozy let out an exasperated sigh and dropped to the ground. "Somewhere in this room," she gestured widely with tired eyes, "Didja happen to see anything showing a cow-lady's boobs blowing up."

She had, to her immense displeasure. "U-um, on the center table," Twilight answered, feeling sick again. "Big rolled-up scroll."

Cozy trotted to the first table Twilight had examined, fished around briefly, and picked up the manuscript of the cow-mare whose udders exploded that had offended her so much. "Look what she's wearin'," she commanded, though thankfully she did not open it all the way to the last panel.

Twilight paled, having failed to notice the cow lady was wearing a black choker with a red cowbell. Her mind clearing from the pain, she vaguely remembered herself gradually approaching the necklace. She hadn't even realized she wasn't talking to herself. Obviously, it must have coaxed her into a submissive fugue state and subtly compelled her towards it. "I almost put that on..?!" she squeaked.

"Yup yup yup! You're lucky the Princesses sent me!" Cozy pouted up at her. "I'm immune to anything in this room, so I can keep you and that steaming swamp under your tail outta trouble."

Twilight dropped her tail, pressing her thighs together and going pigeon-hooved. "The Princess... sent you..?" Twilight blushed, until her mind cleared enough to accept the obvious. "... You're this world's Cozy?"

It made a lot more sense than Cozy escaping an impossible prison and crossing worlds to come kick her in the boobs, of course.

Cozy leaned back with a face like she'd just tasted something sour. "Whattya mean this world's Cozy?"

Twilight sighed. "I'm another world's Twilight. I woke up in your Twilight's body a couple days ago. I'm trying to find a way to fix it, or at least contact her so we can work on it together. I thought the library might have information to help me figure out how we've switched minds, but um..." Her face itched and she looked away. "... I've only found weird boob-related sex stuff..."

"Well you sure seem into it," Cozy scowled.

Frightened and totally out of her comfort zone, Twilight wasn't sure how to respond. She'd always been a rather chaste girl in her own world, and she'd found everything in this library very overwhelming. But she couldn't deny that she had basically begun masturbating in the forbidden section of the library full of potentially deadly boob-curses and that she'd been caught doing so by a filly. She hung her head in immense humiliation.

"So... your world's got another me?" the filly raised an eyebrow, but her eyes softened a bit. Clearly, as she was out and about, this Cozy wasn't as horrible as hers was.

"W-well, yeah," Twilight scratched at her neck uncomfortably, "You look just like her except the hair. But um, ours is kind of... indisposed..."

"Did you kill me?" Cozy gasped.

"What! No! No-no-no," Twilight raised a hoof defensively. "Um, the Princesses and Discord turned you to stone."

"So you killed me," Cozy let some steam out of her nose. "What a thing to do to a little filly! But I guess trying to destroy all the boobs in Tittyquestria is a pretty big offense."

Twilight was pretty sure most mares would be willing to kill someone who was trying to "destroy their boobs", yes.

"You can un-stone ponies," Twilight defended. "But our Cozy tried to destroy all of the magic, yes. We uh, our magic is... rather different in nature. You said you're immune? Is that because you're, um..."

"Not Sweetie Belle?" Cozy glared up at her, blinking once. She lifted one forehoof and waved it under her own body - quite unimpeded - then set it back down, still glaring evenly. Indeed, Sweetie Belle was an early bloomer, and pretty much a miniature, louder Rarity. Both Sweetie Belles had a habit of tripping on themselves - but this world's more so.

"I, I was gonna say a filly," Twilight grimaced. "But sure. Um, thanks for saving me." She paused and thought it over. She hadn't been told anyone would accompany her, but if Cozy was malicious, surely she would've let her put on the boobs-go-boom necklace. "Can you watch my tail while I keep looking?"

"Sure." Cozy smiled. "You know if anything happens I'm gonna kick you in the jugs again, right?"

"C-can you try calling out to me first..?!" she instinctively tensed up and lowered her wings to protect her assets.

"You get three heys before I go for the kill."