Author's Note

All of these are fictional characters, and ones above the age of 18, at that. Consent is sexy, people.

Chapter 1: Featuring dimension hopping, magical explosions, slight TF, and gratuitous nudity.

“Huh. That's interesting.” Twilight Sparkle said. She squinted at the rows upon rows of equations she'd written down, and pushed her glasses further up her nose. She flipped her pen around in her hand, and used the end of it to follow the arcane mathematical symbols as she checked her work.

As she went on, her heart began to beat faster and faster as she realized what she was looking at.

“It's not just the statue at Canterlot High.” She said aloud, and let out a giddy (nearly mad) laugh of discovery. Clutching her notebook, she rushed over to the full-length mirror affixed to the back of her bedroom door. “Any reflective surface can be used as a dimensional gateway, as long as it's properly positioned and calibrated. I should have known!”

Twilight grabbed a dry erase marker from her desk, and immediately set about copying the equations from her notebook onto the edge of the mirror itself. Engrossed in her work, Twilight didn't notice how the symbols she scribbled onto the reflective surface began to faintly ripple as soon as she wrote them. “It's just a matter of attuning this mirror to the resonance frequency of the pony dimension, and … there!”

Twilight scrawled down the last runic equation, and smiled proudly at her handiwork.

That's when the world exploded.

It all hit her at once: enough sound to deafen, enough light to blind, enough force to wrench every atom of Twilight's body apart, and then mash them back together again.

And then, darkness.

Slowly, Twilight felt feeling return to her body. Her head throbbed with the world's worst hangover (not that she'd ever touched alcohol before) and she let out a pained groan.

Faintly, Twilight reminded herself that pain was a good sign-- a sign that she was still alive. Either that, or she'd died and a wince-inducing migraine was to be her punishment for all eternity. Beat fire and pitchforks, at least.

Then again, most hells probably wouldn't have dumped Twilight face-down on a plush, satin-sheeted bed, either. She rolled to her back-- and let out a little mutter of pain as she felt something jabbing uncomfortably at her shoulder blades. Was she in a hospital? Had she gotten hurt in the magical explosion?

Twilight forced her eyes open.

She looked up at a silky canopy-- the sort of bed typically reserved for royal castles instead of hospital rooms. It certainly was a far cry from her cluttered and bookshelf-crammed bedroom at home. Twilight planted her palms against the soft sheets and sat up-- sure enough, she was looking at a lushly appointed bedchamber. Hardwood furnishings, finely woven tapestries, and polished marble along the floor. A wide window led out to a wider balcony, and sunlight streamed through with the promise of a gorgeous day.

“I've done it!” Twilight blurted, giddy. “I've traveled to the pony planet!” She paused, and looked around, making sure nobody was around to hear her error. “Pony dimension, rather.” She cleared her throat, and then scooted off of the empress-sized bed. Her hooves clicked softly against the tiled floor.

Twilight blinked. Hooves?

As she looked down, she came to several important realizations.

One: somehow, the process of dimensional travel had changed her.

Two: she was stark naked.

Twilight felt a warm blush rise in her cheeks-- only to shiver a little as a cool breeze wafted in from the balcony window, ruffling her hair and tail.

Tail?

Twilight twisted around, and, sure enough, there was a luxuriant length of purple-tressed tail jutting out from just above her rump. Scientific curiosity took precedent over embarrassment, and Twilight rushed over to a mirror so she could investigate herself.

“Okay, this is weird.” Twilight stared at her reflection. It felt weird to even refer to it as “her” reflection … as once she got past the hairstyle and the general coloration, the being looking back from the other side of the mirror wasn't anything she was expecting.

Wide-eyed, Twilight leaned towards her reflection, and moved her hands over her own face. Leaf-shaped ears poked out of her purple hair, along with a unicorn's horn at her forehead. She poked the surprisingly solid appendage, and congratulated herself for not making any “I'm horny” jokes. She ran her fingers down over her face, experimentally feeling the soft purple muzzle.

Twilight stepped back, and looked over herself as a whole. Bipedal. Four fingers and an opposable thumb on each hand. A fine coat of purple hair covered her from ear to toe (ear to hoof?) though she still had the purple hair on her head and tail … and, Twilight noted with some slight embarrassment, between her legs.

“But … the other Twilight said she walked on four hooves.” Twilight held a purple hand up before her eyes and wiggled the fingers experimentally. “So … it stands to reason I've found a third dimension. Kind of … halfway between, I guess?”

Twilight turned around, looking over her shoulder at the mirror to size herself up. Sure enough, there was the tail-- and wings. They were folded neatly on her back, but with a slow stretch, Twilight realized she could move them just as naturally as any other part of her body. She gave them a slow flap, feeling the odd, but not unpleasant feel of wind through her feathers. Briefly, Twilight considered seeing how flightworthy this new body really was, but decided against it. The last thing she needed was to accidentally break her neck after discovering a new dimension.

There was some kind of mark on her butt, too. Each cheek had a familiar, geometric starbust design on it. A tattoo? Twilight ran her fingers over the edges of the design, curious. In her examination, she couldn't help but notice said butt was a bit more … full than she'd had back home. She turned around again, and noted the same extra curve in her chest. Twilight bit her lower lip as she sized herself up-- not only was she half-pony in this dimension, but she was also stacked. A lot different from the skinny, not-yet-entirely-filled-out eighteen year old she was used to being. Twilight cupped her breasts, experimentally, and then shivered as her fingers accidentally brushed over her dark-purple nipples.

“Ooookay.” Twilight clapped her hands to her sides. “Similar biology means similar erogenous zones. Lesson learned.”

She shook her head, and decided to investigate the bedroom instead of … herself. Each step sent a little 'click' echoing through the room, as if Twilight were wearing heels. The bedchamber itself had everything one would expect: a writing desk, a door leading to an apartment-sized bathroom, a nightstand with a couple of battered Daring Do paperbacks … and a wardrobe.

“This'll come in handy.” Twilight said, and threw the armoire open-- only to find it surprisingly barren. There were only a handful of hangers, from which dangled a few complicated-looking evening gowns, and then a simple sundress.

Twilight dug around, looking for more clothing (like, say, underwear) but found nothing. “Well, at least I'm not streaking.” She said, and went with the least ostentatious option. The cream colored sundress was cut low in the back, to accommodate her wings … though Twilight couldn't seem to find a place to put her tail. She just let the skirt dangle over the extra appendage … which meant that Twilight's bare bum would be exposed if she lifted her tail by accident. “Better than nothing.“ she mused to herself.

Once she was decent (or at least as decent as she was going to be), Twilight walked out onto the balcony. A fresh spring breeze carried the lovely scents of a blooming forest to her nose-- Twilight breathed deeply, and wondered if her pony-ish anatomy gave her an enhanced sense of smell. She shivered slightly as a draft wafted beneath her skirt, only to clap her hands down on the billowing fabric before she could flash anyone.

Not that there was anyone to flash. She was up in the balcony of some kind of castle, tucked away in a lush, idyllic forest. A valley rolled out ahead of her, and in the distance, she could see a small, but active village of some kind.

“Wow.” Twilight mused. “If only the girls could see this.” And then, another realization struck her. “Wait, they can see this! All I have to do is re-work the equations on another mirror so I can get back home … “ Twilight beamed, and rushed back into the bedroom. “All I need to do is check my notes--” She skidded to a halt a few steps later. “In my notebook. That I don't have. Oh.” She drug her hand over her face. “That's … not a problem. I mean, it only took me a couple of weeks to figure it out, that's all. I mean, I've got pen and paper right here, so that's a start, right? It's not like I'm stuck in an alien dimension in weird body that's probably magical for the rest of my life, right?” The words came faster and faster as she said them-- until Twilight forced herself to breathe and calm down. “Nothing I can't deal with. But first … “ She looked out the window at the sunny spring skies beyond. “A little exploration is in order.”

Twilight didn't find anyone (or would that be anypony?) as she explored the castle. The towering, two-story library tempted her-- but she forced herself to look away, to head out the castle's front door. That could come later-- right now, she needed to get the lay of the land first-hand. (Or would that be first-hoof?).

It was an idyllic late-spring/early summer day, with the sun blazing down merrily from above. Twilight followed a well-worn cobblestone
path out from the front of the castle, leading through a forest as well tended as any private garden.

“Hey Twilight!” said a familiar voice. From above. “I thought you were gonna miss the festival?”

Twilight blinked, and looked around in confusion-- until she saw a small, fluffy white cloud move against the wind 'til it hovered directly above her. A blue muzzle poked from the bottom of the cloud, followed closely by an alien-yet-familiar face, topped with a shock of prism-hued hair.

“Rainbow Dash?” Twilight held a hand up to her mouth.

“In the flesh!” Rainbow Dash said. With the acrobatic grace of a trapeze artist, she slid out of the cloud and twisted around in mid-air, splaying out her seemingly too-small wings to slow herself into a lazy hover a few feet above Twilight.

The casual violation of at least half a dozen laws of physics would have given Twilight pause alone. However, there was also the matter that Rainbow's burst of 'in the flesh' was entirely too literal, as the pegasus-pony-person was bereft of even a single stitch of clothing. Her body was lean and lithe, though not without just enough softness in both hips and bust to show her as unequivocally female.

Not that there was much equivocating to be done on the subject, given Twilight's point of view.

Cheeks flushing, Twilight looked away.

“Sorry!” She blurted.

“For what?” A light breeze ruffled Twilight's hair as Rainbow landed on the ground in front of her. “You haven't even been gone that long!” She paused for a moment, and peered at Twilight. “Saaaaay, what's the occasion? I didn't forget your birthday, did I? 'cause seriously it hasn't been that long and I know you're not that old!”

Twilight blinked, and looked back at Rainbow. At her eyes, that was.

“Occasion?” Twilight said.

“Oh, c'mon!” Rainbow Dash tugged lightly at the fabric of Twilight's sundress. “We both know you wouldn't get all this dressed up for no reason.”

“Uh.” Twilight looked down at herself, and then back up (only catching a glimpse of Rainbow's nude blue body by accident-- or that's what she told herself). “I … just felt like it?” Twilight said, and then coughed slightly. “But … what about you? Don't you feel a little. Um. Cold?”

“Not in this weather. I should know, since I designed it.” No matter what the subject, and no matter what the dimension, Twilight realized Rainbow's braggadocio remained a universal constant.

“Aren't you afraid of somebody, you know … seeing you?”

“Seeing me?” Rainbow Dash furrowed her brow in confusion. “Do I have something on my face? I've got something on my face, don't I?” She rubbed her hands over her muzzle in search of whatever errant smudges that might have been there.

“No, not that.” Twilight blurted. “It's just that, you're … “

“I'm what?” Rainbow Dash crossed her arms over her smallish, navy-peaked breasts. “Super rad? Totally sweet? Crazy awesome?”

“Naked.” Twilight finally blurted. “Really. Really naked.”

“Well duh! Not all of us are fancy-pantsy princesses who can afford fancy-pantsy dresses for every day of the week! Not that Rarity wouldn't make them for me if I asked, but still. Who's got time for getting all dressed up every day? Not me! I got too much awesome stuff to do!” Rainbow Dash flapped her wings a few times and turned an aerial somersault.

Twilight tried to ignore the new and interesting views she got of Rainbow Dash's anatomy through her acrobatics, instead seizing on one name in particular. “Did you just say Rarity?”

“Uh, yeah.” Rainbow Dash halted in mid-air, and peered at Twilight upside-down.

“Purple hair, fashion designer, friend of ours, Rarity?”

“There's only one of her. That's the 'rare' part.” Rainbow Dash flipped back down to her hooves, and laid her hands on Twilight's shoulders. Twilight jumped a little, feeling a pleasurable jolt sweep through her body at the unexpected physical contact. “Are you feeling alright? You're acting kinda weird.”

“It … it's complicated.” Twilight said. “But … just … humor me. Please?”

“Uh, sure.” Rainbow Dash eyed Twilight warily. “But if you ask me, this isn't very funny.”

“It's not supposed to be.” Twilight shut her eyes, thinking. “Let's … let's just start simple. Let's … let's find Rarity. Yes.” Twilight nodded, forming the rudiments of a plan. Despite the mounting number of differences between her home dimension and this one, at least she knew she could still start on her friends.

“Find Rarity?” Rainbow Dash scratched at her head. “That shouldn't be hard. She's probably at her shop.”

“Then that's where we'll go.” Twilight nodded. “Uh, if you can lead me there?”

“Lead you? But you've been there like a million times before!”

“Please?” Twilight's voice cracked, just a little.

Rainbow Dash blinked a few times, and finally nodded as an understanding smile. “Oooooh, now I understand.”

“You do?”

“You just want me to go first so you can look at my butt!” Rainbow Dash broke out laughing.

Twilight gasped in horror. “Rainbow! I'd never--”

“You'd better!” Rainbow Dash started to jog in place (which caused her modest chest to bounce a bit) and turned around. She flagged her multi-hued tail, revealing a set of round, toned cheeks, each bearing a familiar cloudburst plus rainbow-bolt image. “'cause I totally have the best butt in town! Now c'mon!” and with that, Rainbow Dash took off at a jog.

Twilight could do little but follow.