Author's Notes:

This first chapter is a revised version of a previous stand-alone story. It has been edited so that the characters are ponies instead of anthro in addition to a number of changes to the story text, though the overall narrative remains the same.

The soothingly rhythmical clatter of the Canterlot Express steadily making its way down out of the mountains and into the Celestial valley towards Ponyville was usually something that tended to lull Rarity into a pleasant, though typically brief, sleep. Especially if on days like today when she was returning more toward evening after a long and exhausting trip full of business deals and arranging her appointments as one of the single most favored and trusted of royal courtesans.

Tiring though these activities may be, there was a reason Rarity was now able to afford having her own private train car on these increasingly more common excursions to and from the capitol. There was a time, now several years gone, when she had bemoaned the cost of a single spot on a bench in the standard passenger cars. The jostling and stress of the journey never seemed to do any favors for her carefully maintained outfits or fur. Now though, she thought little of paying a hundred times as much for a bit of privacy, quiet, and most importantly, a personal rail car with better quality suspension.

Looking up from her consideration of one of her many personal clothing sketchbooks, this one featuring ideas for a new line of thong underwear, Rarity smiled at the orange glow of the setting sun, now just sinking below the snowcapped jagged ridges of the Western Ranges. The warm light playfully interacting in unexpected ways with the reflective ice and dark rocks of the pinnacles to form quite dramatic shadows in chasms and glinting surfaces from the sheer walls soaring up into the thin clouds about their summits.

Mentally returning to her immediate surroundings, Rarity turned her head to regard the oh-so-convenient private bathroom of her rail car, its walls made of finely polished hardwood panels, just the same as all the rest of the interior. She considered, not for the first time, how much extra the additional luxury of her own bathroom added onto the price she paid at least once a week for the use of this car. She smiled slightly at the irony of repeatedly paying for something she never seemed to use. After all, on these trips she usually had a thick diaper taped tightly between her legs that was even more convenient and, to be honest with herself, far more enjoyable to use. Of course, simply wearing a diaper was for more than the fun of it. No, she had practical reasons as well. After all, the diapers she regularly wore were of her own design, and Rarity felt that it was a borderline sacred commitment on her part that she personally test everything that she sell, whether it be ball gowns or butt plugs. Therefore, whenever she had a new design of diaper in the works, she had to find the time to try it out. The hour-long train ride between Canterlot and Ponyville made for the perfect opportunity to do just that. Not only could she have privacy, but she could try out her newest diaper in just the sort of situation in which many of her customers might well use it. After all, no one had yet seemed to figure out a good way to make using the bathroom on public transportation a relaxing experience without an unfortunate amount of money being required. Her diapers, she hoped, would help solve this problem for many.

This particular train ride was, however, an exception. Rarity was not in fact wearing a diaper at the moment, mostly due to plans she hoped to pursue later on in the night. Though truthfully, the pressure between her legs was beginning to make her wish she was diapered. As much as Rarity longed to simply spread her legs and go where she was, her present outfit made that a difficult prospect. She was currently wearing one of her favorite pairs of black pvc shorts, designed by herself of course. Not only did the smooth and shiny, thick plastic-like material compose the outside of the shorts, but unlike many other, cheaper garments, these had the same material on the inside as well. The tight smooth feeling of the pvc plastic hugging her butt and hips, to say nothing of how it pressed into her pussy and held her long thick dick firmly upright could keep her hard just thinking of it. Despite the shorts being somewhat high-wasted, Rarity was big enough that a good inch of her cock had a habit of sticking past her waistline when she was ‘in the mood’. Her current clothing choices did little to hide this embarrassing side effect of her arousal.

Her choice of outer shirt was a thin translucent, white, nearly sleeveless blouse designed to show off her tank top underneath, a belly-shirt made of the same slick and shiny pvc material as her shorts, and as they really did nothing to hide anything past the top of those shorts, it would make for an awkward situation if she let herself get too hard with many others to see. It wasn’t really as though she was trying to hide the fact that she currently boasted a fine male member in addition to her well looked after natural sex. After all, the clothes she wore never did do much to conceal her typically excited state, it was just that she was not in the habit of trying to push the bounds of public decency too far. Yes, Equestria was a very tolerant nation in such respects, but there were limits, especially where male sex organs were involved. However, as Rarity was arriving home at a time when most ponies had already returned home, she was not overly concerned.

‘Perhaps just a little piss…a small trickle won’t hurt.’ Rarity thought, as, inevitably, she grew more excited at the idea of wetting in such a hot outfit. The sudden short burst of hot urine from her pussy, (oddly enough she could choose which sex organ her pee came out of) made her giggle for just a second as it immediately pooled between her butt cheeks as it found little fabric to absorb into. For some reason, this wetness made Rarity even more aware of the tight, thin strap of shiny blue fabric her t-back thong was made from. She loved how its tightness made the thong pull up along her butt as she walked. Sexy clothing was about so much more than just how they looked. It had to feel amazing as well. A good outfit could make Rarity horny with her eyes closed.

She dared not pee any more, as if she did it would all run right down her legs the moment she stood up, and make for a hard to explain mess on the floor. Plus, Celestia only knew what it would do to the expensive varnish on the wood. No, Rarity would just have to wait to do what she wanted in her smooth, shiny shorts.

The distraction of the warm dampness under her butt was interrupted by the realization that the train was beginning to slow and the lights of the station were becoming visible from just out of sight. Shaking her head to get herself fully back to the present situation, Rarity hopped up, and began collecting and packing her things into her small wheeled suitcase. Once upon a time she had liked to travel with a much larger bag, as she preferred to maximize outfit options at her destination, but improved common sense and her business and apartment location in Canterlot had released her of that burden. A bit of swift work with her horn had her sketchbook, notebook, and various pencils and pens stacked neatly on top of a white hoodie which she had learned was useful in the cooler mountain summers of the capitol. Under that were two emergency diapers, which could either be used for on-the-spot demonstrations for potential customers, or for her own pleasure if she suddenly found herself craving a diaper between her legs. Under the diapers was hidden a balled up double-strap v-string thong that Rarity had dug out of Sweetie Belle’s dirty clothes pile before going on her trip. Rarity loved to go to sleep with the comforting smell of her little sister by holding her thong up next to her face when going to bed. Though of course she first liked to rub it over her hard dick until she came.

Rarity stood next to the window of her private car as the train pulled up alongside the station platform. As this car was the second to last of the train, in font of only the caboose, where it finally pulled up was at the far northern end of the station where the lighting was dim and, hopefully, few others would get out.

Rarity was a bit surprised, though happily so, to see that there were not one but two mares waiting to greet her. There was her twelve-year-old sister Sweetie Belle standing there, looking to Rarity like an angel in the dim light, wearing tight light blue denim short-shorts with a clear plastic belt and nothing else. Apparently, Rarity was glad to see, her lessons on only wearing one item of clothing at a time to help focus attention to it even more had sunk in. Sweetie Belle’s curly violet and pink mane was brushed well and tied back into a ponytail, a new style of hers, and the short white spike of her horn jutted from the top of her forehead added to the look. All this Rarity noted in an instant thanks to her years as a fashion designer and general expert on her little sister.

Equally scrutinized was the larger mare with long wavy, almost curly bright pink hair standing, Rarity was quick to note, very close next to her sister. Pinkie Pie was wearing a light green skirt of some material that shimmered slightly in the light of the nearby platform lamps. This was unusual as Pinkie Pie, like most ponies didn't typically wear anything when out and about. Though it didn't take Rarity long to determine the cause of this unusual behavior. The tell-tail bulge of a thick diaper, while partially concealed by the skirt was nonetheless noticeable, and even if it hadn’t been the half inch of white plastic poking past the skirt’s waistband would have given up the game.

“Hmm… Pinkie in a diaper…again… I’ll have to ask her about this new habit of hers.” Rarity mumbled out loud to herself, smiling.

As soon as the train came to a stop Rarity was on her way out the door. When she had first began to use this luxury service the station had thought to have a personal greeter meet her on the platform as soon as she got off every time, after all, the Canterlot elite always demanded as much, someone had to be there to attend to all their ‘needs’. Rarity had swiftly put an end to that nonsense, she did not like to be carefully watched over by strangers when greeting her sister on the platform. Besides, she was not a needy little poof from the capitol who didn't know a diaper from a dish rag. She very much preferred her independence, thank you very much.

Rarity hadn’t managed three paces across the wooden planks of the station platform before the sound of a filly running and a flurry of violet fur ended with being glommed onto by Sweetie Belle who threw her forelegs about her neck as Rarity nuzzled her back forcefully. In sum, this was admittedly a rather overly dramatic hug as they had only been apart for a day and a half, yet it was a fun little tradition between the two of them nonetheless.

“Hehe, I missed you…” Rarity said as her sister lowered herself back to the platform while the two of them touched horns.

“Missed you too! Was it a fun trip? Better than last time?” Sweetie asked staring up at her sister with those beautiful wide violet eyes.

“Oh yes, much better! More time with the Princesses, less time with the nobles. Plus, I got to finalize a few important business deals. I might buy you something special in celebration. What do you say to that?” Rarity asked Sweetie Belle who was still pressed up next to her.

“Really! Like what?” Sweetie asked with all the unabashed excitement of a filly half her age.

“Patience sis,” Rarity said smiling, “You’ll get to see, I’ll come up with something, something…exciting.”

As Rarity spoke, her right foreleg pressed gently but firmly against Sweetie Belle’s butt cheek through her tight shorts. Rarity felt her already stiff cock grow even more firm and begin to slide above her waist line. Rubbing her sister’s butt was one of Rarity’s favorite secret pass times and never failed to excite her.

As Rarity held her sister against her and gently rubbed her leg against Sweetie’s butt she looked up to see Pinkie Pie still standing there only a few meters away smiling happily and perhaps a tad lustily at the pair of them. Rarity gave her a wink, which Pinkie returned with a little giggle.

As Rarity looked back down a sudden realization struck her.

“Sweetie dear, I don't recognize these shorts you’re wearing, or rather I do, but not from you. These are Applebloom’s aren't they.” Rarity stated more than she asked.

Rarity never missed an opportunity to watch Sweetie Belle and her friends if she could help it. Though most days the three of them didn't wear clothing at all, they were getting to that age when young fillies started to realize that certain types of clothing attracted attention to certain parts of the body. Applebloom with her sexy daisy duke short shorts, Scootaloo every now and again with tight denim overalls and her own sister often in very short denim skirts were enough to make her hard within seconds. Even better were the days when Scootaloo would show up with a diaper on under those little overalls. Rarity knew whenever she saw that, that Scootaloo had been with Rainbow Dash earlier in the day as putting the purple maned filly in diapers was one of Rainbow’s ‘things’ she liked to do with Scootaloo when they had their ‘fun’. Over time, Rarity had made a rather complete mental encyclopedia of all the various items of clothing the three fillys wore. Sweetie Belle was obviously much easier to figure out than the other two due to living under the same roof.
Therefore, it was not surprising that Rarity had not taken long in figuring out that the shorts now gracing the cute butt of the filly wearing them, while similar to several pairs that she herself owned, were not actually hers.

“Um…yah, A.B. let me borrow them yesterday. She said she wanted to see how I looked in them. She said I looked real nice and wanted me to stay in them for the rest of the day… I guess I never took them off.” Sweetie said while looking down, and though Rarity couldn’t see it, blushing as well.

“You said this was yesterday and you never took them off? Did you sleep in them?” Rarity said smiling all the more.

“Kinda…” Sweetie said reluctantly.

Rarity took the opportunity of her sister’s embarrassed silence to change from rubbing Sweetie’s butt to running her hoof down the back seam of her shorts between her butt cheeks and between her legs. Rarity hadn’t gone far before her hoof began to encounter a dampness in the denim. Instead of stopping, Rarity went on further and began to press the end of her hoof upward. The area of moisture encountered was too big to be simply from a wet pussy, especially at Sweetie Belle’s age, no, this was from pee. Lifting her hoof to her nose confirmed what Rarity had already known. Her little sister had wet in her friend’s borrowed shorts, and from the relative lack of moisture and smell, she had done so some hours before and yet chose to stay in the wet shorts anyway.

“Well, aren't you a brave filly, not only did you wet in your friend’s shorts, but you did so knowing there was a good chance your sister would find out. I’m actually rather proud of you, it’s good to know what excites you and to not be embarrassed by it, don't you agree?” Rarity said looking down at her little sis while smoothing the fur around her ears.

“Thanks Rarity, um, actually I was going to change before coming here but Pinkie said I should stay in them…so yah. I did.” Sweetie said trying her best to sound confidant.

“That’s very good advice on Pinkie’s part, you should thank her for it. Though I have to ask, what were the two of you up to earlier then?”

An uncomfortable silence from Sweetie followed that question and when Rarity looked up at Pinkie Pie, still standing nearby watching the two of them all she got was a somewhat sheepish smile and a slightly embarrassed look, an uncommon thing from that mare. With one eyebrow raised Rarity looked back down at her sister who, fidgeting slightly, looked like a dog that had knowingly been slightly too aggressive with the newspaper. Instead of increasing her sister’s discomfort Rarity decided she would just get the details out of Pinkie later.

“In that case, I’m sure that whatever it was, you two had fun. Now Sweetie, stand back and turn around and let sis get a good look at thoes shorts. I want to know how well I agree with Applebloom.”

Doing as she was instructed, Sweetie Belle removed herself from Rarity’s side, stood back a step, and turned herself around. The lighting was dimmer than Rarity would have liked but she could see well enough, and in fact the long shadows in some ways helped to enhance Sweetie Belle’s curves. The denim shorts certainly were wonderfully tight, hugging her hips and skinny yet round butt beautifully. The overall look was in fact rather basic. There were no fancy designs, ornamentations, or unnecessary flaps and frills. There weren't even any back pockets at all. Even the seams were smooth and the light blue denim was worn and faded but nowhere torn. In all, they were perfect for showing off a filly’s curves without distracting from the pony herself with their own flashiness. Perfect shorts for a perfect sister. The, by now, mostly dried urine stain covering the crotch of the shorts and migrating a way back up underneath Sweetie Belle’s tail made Rarity’s dick throb. She wanted nothing more right then than to rub it all over Sweetie’s hot twelve-year-old ass until she came.

Collecting herself, Rarity decided that the best way to continue on without exploding was to keep up the conversation.

“I must say, Applebloom sure was right, you look stunning in those shorts. You should be proud of yourself for looking so nice, and be thankful you have friends who know you so well, you’re making me a very happy sister.” Rarity said as she pressed the bulge in her own shorts with a hoof while contemplating Sweetie’s butt.

“Aww, thanks Rarity! I knew you would like them too, they feel so nice to wear. Applebloom is the best!” Sweetie Belle said happily as she thrust her butt out a bit and wiggled it playfully against Rarity’s left foreleg. Rarity closed her eyes and took a deep breath, promising herself that before the night was through she would have a ‘discussion’ with her little sister about the consequences of teasing her so. Unfortunately, that would have to wait.

“Mmm…that makes your sis feel very good, you know that, don’t you?” Rarity asked bending over Sweetie Belle to whisper in her ear. At the same time she put her hoof up on Sweetie’s hip over where her cutie mark would one day appear as she gently began rubbing her stiff shaft with the other front hoof, sitting back on her back legs as the only way to maintain balance.

“I know you like how this feels too but we need to wait until later if you want to keep having fun. Also, we are keeping Pinkie waiting, which isn’t very nice now is it?” Rarity said, being aware of even her own hypocrisy as she was the one doing the rubbing.

“Ok, ok, I know, but you’re the one who- “

“Yes, I know sis, I’m sorry, I should be better at controlling myself in public, shouldn't I?” Rarity said to Sweetie Belle giving the filly one last forceful push in the butt as a response to Sweetie’s halfheartedly suppressed laugh.

Reluctantly releasing Sweetie Belle, Rarity strode the few quick steps to Pinkie Pie and gave her a light hug. This was immediately returned by another hug from pinkie with about five time the strength, nearly enough to pick Rarity off the ground entirely.

“Ooo! I Missed you so! Lest celebrate your return with-“

“No need Pinkie! Whatever it is, it won’t be necessary.” Rarity said cutting her off. She had enough ‘parties’ to attend the way it was; she was not enthusiastic about the prospect of even more.

“Oh, all right silly!” Pinkie said as she released Rarity from the bear hug.

“Though I’m sure there is something you would like to do, considering the outfit you’re in.” Pinkie said with a hot smile as she slid an oddly dexterous hoof under Rarity and over the still firm shaft of Rarity’s cock through her pvc short-shorts.

Shuddering slightly and considering that as much as Rarity liked where this was going she had to do something to intervene.

“Really Pinkie, not here!” Rarity said making a show of looking around. Nopony seemed to still be anywhere near anymore, but anyone could wander by at any time.

“I think it’s time that we headed home. I have no intentions of staying at this station forever. Come, Sweetie, let’s get going” Rarity called back to her sister.

On their way out of the station, the station master made a small show of bowing to Rarity when he saw her from the windows of the office and coming out to thank her for her continued patronage of the Ponyville Express. While she graciously accepted the thanks, and promised that she had every intention to continue using the train service, she was just a bit annoyed at the unnecessary attention. All she wanted was a quiet walk home in peace, though admittedly it was always nice to be recognized and appreciated. Fortunately, though, the encounter was brief and within a minute they had left the station well behind.

The three of them walked in silence for a bit. The sun had set, and the deep purples and blues of the oncoming nighttime sky were overhead with the planets and brighter stars just becoming visible. The air was warm and still, and the occasional beetle hummed about its business. Rarity kept close to Sweetie Belle’s side as they walked. The love they shared didn’t always need words to be expressed, they simply enjoyed being next to each other. Pinkie Pie for her part hummed to herself and strode happily just in front, swaying her hips a bit more than was completely necessary Rarity thought. However, it was not Pinkie’s hips strictly speaking that held Rarity’s attention.

The bulge around the pink pony’s hips and butt was made plainly obvious to Rarity thanks to the tight glittery skirt the mare in front of her wore. Perhaps to somepony else it would have not been so immediately recognizable, but Rarity knew what she was looking for. If the bulge were not obvious enough, about a centimeter worth of white plastic stuck up above the waist line of the skirt, and sometimes the thick crotch of a diaper could just be seen below the hem of the skirt, though it was too dark to make out if the color of the diaper had been changed. Pinkie obviously wanted Rarity to see what she was wearing with all the subtlety of an earthquake. Even if Pinkie had been working harder to conceal the diaper, Rarity was sure she would have figured it out from the smell. True, it was not strong, and Rarity had not noticed it until being hugged so forcefully back at the station, but it was there. Walking behind Pinkie, Rarity could pick up on the faint stench of a dirty diaper whenever the breeze blew the right way. It was interesting to watch the pink mare as she walked, Rarity had seen a number of her customers come to her to purchase a new set of diapers while wearing an already wet one themselves. Often, there was a bit of a waddle to their movements, almost a natural reaction to the thick padding between their legs. Pinkie however, showed no sign of caring whatsoever. She walked quite normally, aside from the sexy hip motions, she might have been wearing a thong for all the restriction to her movements she displayed.

Rarity glanced down to her sister trotting alongside to the left. Was she watching too? She must be able to smell Pinkie. Heck, they had probably been together for hours already, she had to know. To her surprise, Rarity caught her sister staring at her, or more specifically at her hip, or butt, it was hard to tell. She could understand why, as she walked, the dim light of the occasional lantern and the whiter light from the rising moon made her slick pvc jeans-style short shorts reflect that light in beautiful undulating ways showing off the roundness of the healthy mare’s body tightly enclosed underneath. Glancing quickly behind to make sure no one was anywhere in sight Rarity spoke quietly to her sister.

“Looks like you are enjoying what you see.” Rarity said, making Sweetie Belle start a bit and then look away apparently embarrassed.

“Don’t be shy now, I’m your sister, not some mare off the street. Here let me help you.”

Rarity halted her walk briefly and hooked one of Sweetie Belle’s legs with her own and lifted it up and behind her. She then placed that hoof firmly on her butt and held it there. After a few seconds of Sweetie holding her hoof in place the two of them resumed walking onward in silence, Pinkie having not seemed to notice her companions momentary pause. Still without a word, Sweetie Belle soon moved to walk even closer to her sister and pressed her cheek up against Rarity’s thigh as they continued walking. Due to the wonderful ability for pvc plastic to easily transfer heat, Rarity could immediately feel the warmth of Sweetie’s cheek on her thigh as it gently bumped against her as she walked. The feeling was subtle, yet so full of enjoyment that Rarity had to keep herself from stopping right there and making out with her lovely little sister. But the quiet sexiness of the situation was a joy to experience in its own right.

It didn’t take more than a minute or two before Rarity saw out of the corner of her eye a soft green glow form around Sweetie Belle’s horn and a slight tingling sensation just below her waistline in back. Su re enough, as she had guessed she would, she felt the magical pull hook onto the back of her thong just where the straps made a ‘T’. Just a few small tugs made Rarity shiver and she looked down ruefully as she heard a small giggle. She paused in her trot once more and reached her front right leg around Sweetie Belle’s shoulder and hugged her close to her side as the inquisitive magic went back to roaming over her butt. Rarity couldn’t help but briefly muse on the fact that her little sister got to do for free what many mares in Canterlot and a few other cities paid hoovesomely for.

Lost in their mutual fun, Rarity was almost surprised when she suddenly realized that they were getting quite close to Carousel Boutique, the original home of Rarity’s expanding business empire, having walked nearly all the way across Ponyville, not that such a walk was a particularly long one however, as Ponyville was still lost somewhere in that nebulous realm between being regarded as a large village or as a small town.

Rarity also realized that Pinkie was still with them, having led them the whole way. Apparently, they had business to discuss before parting ways she decided. Otherwise the pink pony would have mysteriously vanished somewhere along their route as she had an occasional habit of doing.

“Go on inside Sweetie Belle, Pinkie and I have grown-up stuff to talk about. I’ll be along in just a minute.” Rarity said, detaching herself from her sister.

“Aww… I wanted to watch…” Sweetie Belle said, somewhat under her breath.

A raised eyebrow from Rarity was all the motivation Sweetie Belle needed to do as instructed. Perhaps though, someday, maybe someday soon, she could watch. Rarity considered this, looking on as the small form of her little sister ran up the steps and opened the front door, Rarity smiled with love for the young filly. Soon enough warm light was spilling out from behind the front curtains and onto the porch where the two stood.

“You and I have a thing or two to discuss, Pinkie.” Rarity said with a sly smile.

Pressing her hips up against pinkie’s in a similar movement to what she had recently done with her sister, Rarity led Pinkie around the circular porch of the structure to the back of the boutique and to a back door that led directly into Rarity’s private work room, in which she always kept a light on. Unlocking the outside door for the both of them, Rarity looked inside and noted that she had locked the inner door as well, the one that led into the boutique proper. Out behind them stretched several acres of farm fields and behind those, the dark outline of a forest. That was one of the nice things about living on the edge of town in Rarity’s opinion. Fewer folks to always be watching you.

As soon as the two mares came inside and the bolt on the door was securely fastened, Rarity immediately turned and kissed Pinkie hard, pushing her tongue between the mare’s teeth and licking every crevice she could get to with it. Pinkie of course, happily accepted the intrusion and returned the favor. She also grabbed Rarity’s slick pvc covered butt and squeezed excitedly. Almost as soon as Rarity began she pulled away. And set pinkie with a stern look.

“So what exactly is it that you are wearing under that skirt of yours?” Rarity asked in mock anger.

“I’ve been able to smell it ever since I laid eyes on you this evening.”

“Hehe, they’re my favorite kind of underwear Rarity! Would you like to see? Diapers are the best, most wonderful thing ever! Here, what do you think?” The pink mare asked excitedly.

For a brief second Rarity mused that in this statement Pinkie was, as the saying went, preaching to the choir.

Lifting the back of her skirt, with a foreleg Pinkie treated Rarity to a very naughty sight. A thick disposable diaper, heavily swollen with pee, yet taped tight enough so as to not sag much was covering all of Pinkie’s round butt. The diaper was large enough and Pinkie still slim enough that the padding even wrapped over most of her thighs partially obscuring her cutie marks. It took Rarity no time at all to identify the diaper as one of her own manufacture with its subtle classy design of silver lines running around the leg holes and the front clear plastic tape guard or ‘landing strip’ with its small silver star pattern, along with the light pink of the sides of the diaper, which were designed to accentuate the white front and back. Or rather, a front and back that would have originally been white.

Upon closer inspection, the front was not discolored just by urine but there was actually a slight brown hue to it. The first question to Rarity’s mind was how long had Pinkie been in this diaper and how much had she used it? Without thinking Rarity brought her leg up and pressed a hoof into the thick, soaked and apparently messy padding of the back of the diaper. Feeling the warmth of the diaper combined with the smooth plastic of its surface seemed to send a direct message to Rarity’s member making it stand to attention. Pinkie simply smiled over her shoulder at Rarity’s hoof and wiggled her diapered butt in a non-verbal attempt to get Rarity to move her hoof about more.

“I need to see what’s inside that diaper, Pinkie. In fact, what I really want… is to be inside of that diaper.”

“Oh, Rarity! I thought you’d never ask!” Pinkie said with her customary delight.

“Diapers are the best thing ever! I know I already said that but it’s so true, I love wearing my very own toilet and peeing in it! And pooping in it! And squishing it all over! And they are even better when you get to have sex in them!”

Pinkie continued without pause while already in the process of tugging off her skirt and laying it out on the polished wood floor of the small room. It hardly made for much protection from the hard wood due to its thin material but neither Pinkie nor Rarity were in munch of a mood to care about such trivial matters.

As soon as her skirt was laid out Pinkie Pie sat down heavily on it with an audible squish and a moan of pleasure. Now Rarity was desperate to find out what all Pinkie had done in her diaper to cause such a sound. She began to peel off her tight pvc shorts now that she was sure that whatever was going to happen over the next few minutes her rock-hard shaft was going to require unrestricted motion. Though Rarity couldn’t help feeling slightly disappointed as she peeled off the smooth plastic shorts. She did love how they felt on her. But unfortunately, this was not a ‘have her cake and eat it too’ situation.

Pinkie watched with interest as Rarity’s dick was freed from its confines and bobbed about enticingly. Rarity’s skimpy thong, though doing nothing to contain her shaft did still cover her two heavy, smooth balls, and her dripping clit. As Rarity carefully folded her shorts and laid them carefully on a nearby table (she refused to treat them without respect no matter the situation) she decided to keep her thong on, after all, she liked how it felt running up her butt.

Soon Pinkie began to tug at the tapes holding the diaper firmly in place about her body, but Rarity decided she wanted more control over the situation.

“Here, let me do that, you just lie back and relax, Pinkie, let mommy do the work.”

“Ooo… Ok, ‘mommy’, come check out Pinkie’s messy diaper!” Pinkie said as she lay back onto the floor with her diapered butt positioned directly over the skirt she had laid out

“My pleasure pinkie, I see you have on one of the diapers I gave to you a while back and I want to see how well it has stood up to some obvious heavy use.”

Rarity could have used her horn for such a task, but when it came to diapers she was very much a hoofs-on kind of gal. Sitting down right in front of Pinkie, Rarity first laid both her fore-hooves on the front of the stinky bulging diaper and enjoyed the warm smoothness of the plastic. She was proud to see that even though obvious brown stains had appeared all around the leg holes of the diaper and were creeping up and over the front, there had been little to no leaking. Perhaps there was a bit of poop visible in the fur between Pinkie’s inner thighs and the diaper, but not much. Unable to help herself, Rarity leaned forward and kissed the front of the diaper, reveling in the smell it gave off. This made the mare wearing the filthy thing giggle playfully as she gave Rarity’s head a quick squeeze with her legs.

Slowly pulling on the fastening tapes so as not to damage them in any way Rarity released the front of the diaper and pulled it off of Pinkie letting it plop down heavily in front of her. The sight of most of the diaper, along with the majority of Pinkie that had been under said diaper coated in a slick layer of brown paste that glistened in the lamp light made Rarity grin wickedly. This was even more messy than expected, and she had expected a lot. Furthermore, it occurred to her sensitive nose that the smell from the diaper was perhaps not just from a recent mess but from poop older than only a few hours.

“Oh, my. Pinkie…tell me dear, how long has it been since you changed into this diaper?” Rarity asked. Expecting, and honestly hoping, she was correct in her assumption.

“Umm, let’s see now, I put this one on late on Wednesday night before going to bed.” Pinkie said, making a show of being very thoughtful about it.

‘A day and a half! In the same messy diaper! Pinkie must be immune to diaper rash.’ thought Rarity, somewhat enviously. Though, she considered…had she ever tried staying in a messy diaper quite that long? She decided she had not. Perhaps and experiment was in order.

“And, uh, how many times have you messed it?” Rarity asked while placing her other hoof over the shaft of her cock while staring at the outline of the pink mare’s pussy, now slick with poop.

“Well, I made a big runny poop right after I put it on before going to sleep, then another one after breakfast yesterday, then again last night, and again earlier this afternoon… So four times I guess? And I always made sure to squish it around lots and lots to make room for the next load! That's why I like your diapers so much Rarity! They can hold so much! I’ve lost count of how many times I wet it too,”

Rarity shook her head in amazement. And she thought she stayed in her messy diapers a long time, sometimes most of the day, but here was a pony who was taking things rather further.

And that made her incredibly horny.

“Pinkie, please let me fuck you, please?” Said Rarity almost desperately.

“Silly! What do you think I’m laying here for! Dirty diaper sex is what every filly needs!”

Without even bothering with a verbal reply to such a statement Rarity slid her legs under Pinkie’s, pressed the head of her leaking shaft against the shit smeared pussy before her, and with a single swift movement she was suddenly all the way inside the dirty mare, to the point that her balls were pressed up into the poopy mess coating Pinkie’s crotch, and her own pussy was squished into the messy padding of the diaper below her.

A pair of deep moans sounded out through the walls and into the still night air of the countryside behind the boutique. Articulate comments were hard for either of the mares to express as they worked at adjusting their positions.

“Ohh… Pinkie, how do you stay so delightfully tight?” Asked Rarity as she began to pull herself about halfway out of Pinkie Pie before thrusting herself back in, the warm shit coating her slick shaft making for an excellent lubricant.

“I’m not that tight silly! You’re just so big!” Pinkie said laughing, as Rarity’s thrusts made wet squishing sounds.

“Perhaps I am, but I still think you’re tight anyway, which is amazing considering how often you have things inside of you.”

Pinkie’s response to that statement disappeared in a series of grunts and moans as she lost her desire, or ability, to continue the conversation. Her body was now glistening with sweat as she repeatedly took in the full length of Rarity’s wonderfully large member, the same member that had been granted to Rarity by Princess Cadance and subsequently used on half the mares in Canterlot, if any of the stories were to be believed.

Even Rarity had given up on trying to carry on with the conversation, lost as she was in the feel and sight and certainly the smell of having hot, wet sex with a mare in an overly used diaper. The sensations reminded Rarity vividly of her experiences being babysat as a young filly by a teenage mare who thought it fun to let Rarity simply stay in her diapers, which she wore until she had been almost nine, long after she had both wet and messed in them. Far from trying to be cruel, the babysitter, who’s name Rarity had embarrassingly forgotten, had realized that she liked how her diapers felt when used, and decided to not interfere with the filly’s pleasure. Even going so far as to let young Rarity bounce her poopy butt on the young mare’s back, spreading her mess all over in her diaper. Even today, Rarity still got horny remembering the way the poop felt being squished around between her legs as she ran around her parent’s back yard. She could also remember how the babysitter would occasionally come around and put her hoof on the front or back of Rarity’s diaper and thoroughly feel all over the outside to check if Rarity had used it or not despite knowing full well she had used it some time ago.

None of these memories however, were being consciously recalled as Rarity swiftly headed towards orgasm. It was embarrassing really, how fast she was ready to cum. After all, she was a practiced expert at making sex last precisely as long as she wanted to and not a second less. However, she usually had not just spent the last half hour doing sexy things with her little sister or fucking a mare who had been in a poopy diaper for two days straight. Plain sex was far more easy for her to deal with in terms of still being able to think logically. This situation however, was simply too much to take. Her cock had been desperate ever since she had first saw her sister and Pinkie on the station platform, and since, in Rarity’s opinion, her sister’s body was still too young to take her inside, Pinkie had been the logical eventual partner of the night.

Giving up on her thoughts of trying to control herself, Rarity simply erupted deep inside of Pinkie, her cum a hot gooey torrent, each ejaculation accompanied by groans from both mares and eventually a yell from Pinkie as she herself came, spraying clear fluid all over Rarity’s poop smeared balls. Rarity didn’t let that be an excuse to stop, instead she simply used the new slimy feeling of her own cum, now helping to fill Pinkie, to bring herself to orgasm a second time in as many minutes. Pinkie, for her part, happily went along for the ride, moaning for all she was worth, while Rarity’s deep thrusts repeatedly squished the pink mare’s butt back and forth in the mess of her diaper.

Having finally spent herself, Rarity lowered her body down onto Pinkie Pie, the both of them still breathing heavily.

“So, I’m guessing you liked that.” Rarity said before parting Pinkie’s lips in a short but deep kiss.

“Oh, just a little!” Pinkie said laughing.

“But maybe next time you should be the one in the diaper and I’ll have the cock!”

“That does sound marvelous dear, but you’ll have to ask Cadance or, if you’re brave enough, Luna, if you want a member like mine. I’m afraid I don’t have the magical ‘finesse’ as it were to create my own.” Rarity replied seeming almost disappointed.

“Oh, don’t feel bad Rarity, just be glad you have one to stick inside so many ladies anyway! I don’t care who made it, as long as it fills me up!”

“Stick inside…” Rarity repeated, thrown off her train of thought by the crassness of the comment.

“Well, so much for expecting elegant comments from that one.” Rarity mumbled to herself, though loud enough for Pinkie to hear anyway.

“So um, Rarity, assuming you’ve blown you’re load in me as much as you wanted to… could you tape me back up in my diaper? Please?” The Pink haired mare asked, looking as innocent as it was possible for her to do.

“Really Pinkie?” Rarity asked staring down at the mare under her, watching as a goopy stream of her own white cum seeped out of Pinkie’s pussy and pooled into the brown muck coating the insides of the diaper.

“You still want to stay in that thing?”

“Well of course silly pants! It’s not like its falling apart yet or anything, and it’s not leaking either! Well…very much. Anyway, the more I use it the better it feels.” Pinkie stated quite matter-of-factly.

Shaking her head, Rarity sighed and, again, preferring to use her hooves for such things, lifted the front of the diaper, which she found to be surprisingly heavy, and folded it over back onto the mare lying on it. Pinkie groaned and wiggled herself around a bit as the now cooled squishy mess came back into contact with her crotch and lower stomach. Rarity made it a point to pull the tapes as tight as she thought the diaper could take. After all, if Pinkie was going to keep on wearing the filthy thing, then it might as well be taped up right.

“Pinkie! Hold still.” Rarity admonished as the diapered filly wriggled her hips about trying to get as much sensation as possible from her movements as the messy diaper was pulled up tight around her.

“Sorry Rarity, it just feels so good on me, especially feeling all your cum mixed in with my mess!”

Sighing, Rarity admitted to herself that Pinkie’s actions, despite being frustrating at times, and, no doubt her words, were making her get hard again.

‘Too late for a third time, I need to get ready for tonight.’ Rarity thought.

“There! All done. Now you can enjoy your, ah, old and extra dirty diaper…again.” Rarity said somewhat dryly. As she finished getting Pinkie back in her quite well used padding.

“Oh, thank you so much Rarity! I feel great inside and out now, thanks to all your cum squishing around deep inside my pussy!” Pinkie said standing up and stretching.

Rarity had to admit that the way the diaper’s smooth plastic wrinkled around the tight tapes and the way the discolored diaper bulged out so full of pee and mess really was rather enticing. It was a sign of how well the diaper fit Pinkie no matter how thoroughly it had been used.

“But I gotta get going, it’s about bedtime for the twins now and they always sleep better when they can sleep with me.”

“Don’t tell me you’re going to sleep with those two while wearing that thing. Won’t the Cakes be angry? You won’t be setting a good example if the twins’ potty training is supposed to stick.” Rarity said with mild concern.

“Ok, then! I won’t tell you then!” Pinkie said, while a mischievous smile spread over her face.

“Anyway the twins wear diapers at night besides, so they might as well learn to enjoy them, right?” Pinkie continued.

“Just…don't do anything too, I don’t know…dirty, with them.” Rarity said, wondering at the double meaning in her own statement.

“Rarity!” Pinkie exclaimed in mock offense.

“I’m the most trustworthy and diaper-experienced mare you could hope for!” I’m perfect for the job!”

“Of course you are Pinkie.” Rarity said, smiling, white doing everything she could think of to not roll her eyes.

“Thanks again Rarity, you’re the best! And next time…” Pinkie said taking one of Rarity’s hooves and pressing it firmly against the back of her diaper, which made a wet squelching sound, while reaching out her own hoof and firmly taking hold of Rarity’s still exposed and still quite stiff dick.

“I want you up inside my butt as far as you can go while I try to poop at the same time. I want to see if I can still use the bathroom during anal sex. Have always been curious ‘bout that!” Pinkie said, suddenly shifting from sounding sexy to her more typical, bubbly personality.

“Bye now!” Pinkie said, quickly turning and heading out the same back entrance they had come in only minutes before while at the same time pulling on her skirt.

Rarity, suddenly standing alone in her private work room could only shake her head at the amazing, though so very odd friends she had made over the years.

As she strode over to retrieve her shorts from the counter she had placed them on, Rarity was suddenly struck with the realization that she had to pee, and quite badly at that.

‘Damn, of course I’d only have to pee after Pinkie left. If that crazy pony had only stayed two minutes longer I could have gone in her diaper or even insider her…’ Rarity contemplated.

‘Ah well, no use thinking on it now…’ Rarity decided, somewhat frustrated.

Leaving her workroom, now with windows open to let it recover from the stench of Pinkie’s diaper, Rarity quietly padded barefoot through the darkness of her boutique. The mess she had acquired from the diaper of the mare she had just fucked formed a thin slick layer over her cock and between her legs, which she found herself quite enjoying as the night was a tad muggy and the wetness between her legs was helping her cool off. As she turned and was about to ascend the stairs up to her private rooms on the second floor of the circular structure the silhouette of a still, curved form laying on the sofa under the far window caught her eye. Pausing, then changing direction towards the sofa, Rarity, on silent feet, went to investigate. The soft silver moonlight through the window reveled the sleeping form of Sweetie Belle. She was lying on her side, with her legs tucked in next to her. The filly must really have been tired to have gone to sleep so quickly after getting back despite her knowing, to some degree, what her older sister and Pinkie were up to. Her eyes slightly damp from gazing down upon the innocent beauty of her little sister, Rarity was quick to realize that the filly was still wearing the same faded jeans shorts that she had been in all evening. Apparently being wet in her friend’s shorts was just as pleasant of a thing to do while sleeping as it was while being awake.

“What’s this?” Rarity quietly asked herself, leaning over her sister. The moonlight, while dim, did a good job of showing Sweetie’s skinny, but nicely rounded butt being hugged tightly by Applebloom’s shorts. Now however, there was much more than a faint damp patch between her legs. Half of her butt was darker than the other half, having been recently wetted, with the filly’s urine no doubt. Rarity, intrigued, considered this a moment. If Sweetie Belle had wet them while laying on her side, that would account for the uneven dampness, meaning she had peed after laying down.

“I wonder if she wet on purpose or legitimately ‘wet the bed’ so to speak?” Rarity mumbled to herself, considering the implications. Either way the sight before her, while adorable, somehow made Rarity’s member stand to attention once again.

Along with her newly returned sexual vigor, Rarity was also painfully reminded of her need to urinate and soon. Returning her stare to her little sister and noting the thick clear plastic sheet protecting the sofa from just this sort of occurrence, a wide smile split the mare’s face. Rarity was a mare that liked projects and chores to be completed fully and without parts left undone. Therefore, while seeing half of Sweetie Belle’s butt newly soaked with pee was a very adorably sexual thing for Rarity, it was also somewhat frustrating. It seemed a job incomplete somehow.

Fortunately, Rarity had just what she needed to complete the task, and if Sweetie Belle did wake up because of it, Rarity doubted very much the filly would mind.

Positioning herself properly, Rarity held her now quite hard shaft over her sister and aimed it at the part of Sweetie’s butt that was more or less dry. She leaned over her little sister to get the head of her cock only inches from the smooth denim-covered butt before her. Rarity did not want a long arc of piss that would splatter everywhere and potentially get the walls or floor dirty. She was not in a mood to clean up anything more aside from herself tonight.

Relaxing with a soft sigh, Rarity released her hold on her bladder and let the stream of piss shoot along the length of her cock to spray forcefully onto the cute booty laying just below. The amount of piss in her stream almost immediately soaked Sweetie’s left butt cheek and then began to seep down over her thighs and in between her legs. Soon enough the wetness of her butt was quite equally distributed, much to Rarity’s pride. Despite having accomplished her immediate goal, Rarity wasn’t done pissing and so moved her stream directly to the center of Sweetie’s butt and continued to let it flow for as long as it would.

As her stream finally dribbled to an end, Sweetie’s borrowed shorts glistened in the moonlight from all the pee soaking them. Rarity could also see the small pond of pee that the filly was now laying in. As Sweetie had not apparently awoken from Rarity’s activities, Rarity wondered if the filly would sleep in it all night. Before Rarity recognized she was going it she had her hoof firmly holding onto her shaft and was rubbing up and down along it length.

‘Just like a horny colt’ Rarity thought, bemused at the act of what was effectively simple masturbation. Something that actually she vary rarely ever did as it was not difficult for her to arrange an actual sexual encounter when she found herself horny enough to need release.

Having admitted as much though, the sight before her that had brought her to this sudden strong need to cum, and cum now, was, indeed quite impressively sexy, and worth the private embarrassment.

With humiliating swiftness, Rarity’s slick, sliding hoof caused a thick shower of cum to burst forth and splatter all over Sweetie Belle’s soaked butt, the drops of cum on her upper back sparkling in the moonlight. Sighing, Rarity knelt to gaze at Sweetie Belle’s face in the near darkness.

“You're the best sister anyone could possibly hope for, and I love you so much.” Rarity said quietly to the sleeping filly. After a second, one eye opened just a little to peek out at Rarity.

“Thanks Rarity, You’re awesome too…” A sleepy filly’s voice said.

Rarity, surprised and yet in a way not, at the revelation that the filly was indeed awake if only just, slowly retreated while grinning with both love and amusement.

Before turning and leaving the drenched filly to her wet sleep, Rarity reached out a hoof and gently rubbed the soaked jeans shorts on the butt of the greatest little sister in the world.