Dream Cycle - Celly and Lulu

The pair hurried up to the gym, only to turn a corner and hear a shout. “Hey! You two should know there's no running in the halls!” They came skidding to a halt, Lulu bumping into Celly's diaper at the sudden stop. Standing in front of them in the hall was Rainbow Dash, one who looked just as oddly puffy, and uncharacteristically pudgy for such an athletic pony. Rainbow Dash smirked down at them, “A little too excited for gym class. You don't even have your uniforms on!” She said.

Lulu tilted her head in confusion a bit. “What? We're in our uniforms right now!” She said, shaking her rump a bit unconsciously to prove her point.

“Sure, your class uniforms. You think you can do a triple somersault back flip double double whipless mochaccino half caf in those dresses?”

Celly was about to say she wasn't even sure she could do that even if she wasn't wearing a diaper that restricted her movement, but Dash continued before she could interject.

“Now hurry up to the locker rooms and get into your gym clothes. We only have so much time in the day!” Dash turned about, starting to waddle towards the double doors of the gymnasium, leaving Celly and Lulu to waddle into the locker room.

“Wait, how are we supposed to know which locker is ours?” Lulu asked. Celly shrugged, waddling around until she spotted a pair, each one printed with their respective cutie-marks. She opened the locker, finding a folded up uniform inside. She unfurled it, finding a one piece outfit, something similar to a one piece swimsuit, but a bit more... rubbery.

“That's a uniform?” Lulu asked. “It looks like a swimming uniform, maybe…”

“Well… I know what you mean,” Celly admitted. “But if Rainbow Dash says they're what we should wear, I guess that's what we should wear?”

She frowned. “Do we take the rest of our uniforms off?”

“I'm… hm,” Lulu replied, thinking about it. “Well, we need to take the skirts and the vests off. But the… well, the diaper?”

Celly thought about it. “Maybe… maybe we should try with the diaper, and then if it doesn't fit we should try without?”

“Why not the other way around?” Lulu asked.

“It'd take too long to retape the diaper if we guessed wrong,” Celly replied, frowning for a moment before nodding to herself.

That seemed to make sense… right?

She took her skirt off, then the vest of her uniform, and hung them both up before levitating the rubbery-seeming suit with her magic and starting to put it on. It was stretchy enough that she didn't have much trouble fitting into it, though the elastic-y rubber-y pressure it produced on her diaper felt snug and oddly pleasing.

When she stood up to check how it looked, there was a loud squeak which made her flush slightly – though she couldn't avoid a giggle when the same thing happened to Lulu.

Lulu blushed and stuck her tongue out at Celly, stuffing her normal uniform into the locker. The two headed out of the locker room into the gym where Dash was waiting.

The pony was setting up some miniature trampolines, bouncing a little bit on one of them to get a feel for it. "Alright, you two ready? Or did you forget to stretch too?"

Celly looked a little sheepish, embarrassed she was forgetting so many things today. Lulu was equally embarrassed, though she was still focused on the feeling of her suit squeezing her diaper.

"You can't get ready without stretching, you know! Things grow the biggest when they stretch first!"

Dash stood on her hind legs, reaching into the air. "Come on, we'll start with the simple ones. Reeeeeaaaaach up!"

Celly and Lulu carefully balanced on their hind hooves. Not an easy task given the bulk of their diapers. They stretched upwards, suits letting out several loud squeaks and creaks.

"aaaaand, down!"

Dash bent over, reaching for her hooves and shaking her butt around.

Deciding it was better to do just what Dash suggested than to get it half-wrong, Celly and Lulu shook their own crinkly butts around to copy her – producing a chorus of squeaks and creaks.

“That's more like it!” Dash told them. “Now, do that again!”

She got to all four hooves and watched as they repeated the squeaky, creaky stretches, then nodded. “Great! Next, you have to go on all fours and lean forwards with your back legs – with your wings out and your front legs forwards. Then you reverse it, bending down so you put your head down and your hips up – but all without taking a hoof off the ground!”

She demonstrated, stretching first forwards and then back. The forwards movement looked fairly normal, but the backwards movement stuck her diaper out and she took the opportunity to wiggle it back and forth.

A little hesitantly, Celly and Lulu both followed along. Once again they did the full stretch – forwards, then back, complete with a crinkly wiggle at the end.

“There you go!” Dash announced. “Now, let's get on to the actual exercise! Ready by the trampolines!”

Celly and Lulu each stepped up to their respective trampolines as Dash took her position in front of them. “First up, some bouncing!” Dash said, jumping up onto the trampoline. She bent her legs a bit upon landing, building up a steady rhythm of bouncing upon the stretchy material. It wasn't enough for her to become airborne, but she slowly oscillated up and down in front of them as her tail swished back and forth. The two fillies each hopped up onto the trampolines, Lulu stumbling ever so slightly from the lack of support. The trampoline was much less taut than she had expected, sinking down towards the floor. Both of them carefully shifted their weight and bent their knees, getting into the same beat as Dash in front of them.

“And up! And down!” Dash said, jumping a few inches into the air. Celly and Lulu followed, their legs wobbling upon landing a bit as they got used to the trampoline's surface. “And up! And down!” Dash repeated, jumping up once again. Celly and Lulu continued to bounce, slowly becoming more and more adept. It became easier the less they thought about trying to land properly and just letting themselves enjoy the simple pleasure of bouncing up and down. Listening to Dash's repeated commands certainly helped as well, only needing to do what they were told, and not need to worry about why they needed to. Up and down. Up and down. Up and down.

Dash grabbed her hind legs, starting to bounce her butt on the trampoline, which Celly and Lulu mirrored perfectly. Their diapers sank deeper into the trampoline as they bounced higher, giggling to themselves as their rumps were squeezed with each landing.

Up and down.

The sisters bounced and crinkled, finding it easier and easier to lose focus.

Up and down.

Learning to exercise in a simple, fun way, one which made the best use of their crinkly diapers.

Up and down.

Listening to exactly what Rainbow Dash had to tell them in their lesson.

Up and down.

How they had to listen to the pony who was teaching them, and how they had to keep bouncing.

Up and down.

Dash was talking about other things, as well, but Celly couldn't hear them very well as she bounced

Up and down

Lulu was having trouble keeping track as well, and she didn't see much reason to do anything other than just bounce

Up and down

Up and down…

Enjoying it more every time they bounced up, feeling the plush squeeze of the diaper, and anticipating when they would go

down

and become more and more scattered, finding it so hard to focus, so easy to just do what Dash said… to take in what Dash told them…

up and down…

“Great!” Dash told them brightly. “You really got up to speed with what we were doing! I'm impressed!”

“I, um… huh?” Celly blinked, finding herself on the floor of the gym – still bouncing up and down a little, her diaper wiggling in sympathy with her movements. “I… don't really remember a lot of the lesson...”

“Nah, that's fine,” Dash waved off, smirking. “It means you're really focusing properly on the workout, not bothering to do something silly like remember all the details...”

Celly and Lulu continued to bounce in place gently, their diapers crinkling as their suits squeaked with each wriggle and squish. “Now, let's move on to the acrobatics unit!” Dash said proudly, trotting over to a set of ropes, trapezes, and balance beams that Lulu certainly didn't remember seeing when they had first walked into the room. Dash took her place at the start of the course, showing off everything. “You should already know what to do if you were paying attention during our last exercise, so just get started and I'll grade you on your performance!” She said, smirking just a bit. Both Celly and Lulu looked at each other, their bouncing slowing just a bit. Neither of them remembered what it was they were going to be graded on, and the course looked horribly daunting. “Lulu, why don't you go first?” Dash suggested.

Lulu jumped a bit before she got to her hooves, waddling over to the course. The first part was a balance beam over what looked like a shallow ball bit, and Lulu gulped. “Alright, remember, time's part of it too! But finesse comes first! And... go!” Dash said.

Lulu climbed up the steps to the balance beam, waddling out onto it. She wobbled in place, the poof of her diaper doing nothing to help her. “Alright, show us a prancy pony!” Dash said. As she stood wondering what in Equestria she was supposed to be doing, she suddenly had the urge to try a flip. She had no idea why, she was sure if she attempted it she'd fall into the pit below, but…

Lulu found herself standing on her hind hooves, legs pressing snugly into her diaper to stay on the thin beam. She bent down before pushing up, spinning in the and landing expertly. “Nicely done, Lulu!” Dash congratulated her. “Show us another prancy pony!”

This time Lulu did a slightly different move, adjusted for how she was stood on the beam, and flipped over before landing with a squeak, creak and a thump of her hooves against the bar.

It felt… just so natural to do it. Dash's words were just athletics jargon, right?

...but it was jargon she understood on a deep level, for some reason, so…

Lulu shook her head, wobbling noticeably on the beam, and resolved to focus on what she was doing rather than try to think about silly thoughts that would distract her.

“Let's try something a bit more ambitious!” Dash said. “A fantastic frilly flash!”

The name of the move made Lulu blush, but she was already doing it – balancing on one hoof, shaking her rump back and forth, and flaunting her crinkly diaper to an invisible crowd.

It made her feel like she was doing exactly what she was supposed to, regardless of her blushes, and she felt proud about it…

...as, watching, Celly felt some apprehension about the idea of doing just the same things. Along with more than a bit of jealousy, as well – she felt like it would clearly be enjoyable to do just that, to do her own gymnastic moves.

All the same, she didn't really have any idea what those moves were… she could see Lulu performing them very easily, but she just didn't know how she'd do them herself.

“And dismount!” Dash called, and Lulu jumped off the end of the beam before bouncing once on her diaper and coming to a stop with a crinkle-squeak. “Great! Now, your turn, Celly!”

A little uncertainly, Celly stepped up onto the beam.

“Now, first up, let's see a prancy pony!” Dash called.

Celly tried to copy what Lulu had done, tripped, and fell straight into the ball-pit with a rustle of plastic balls.

Her head broke the surface of the balls and she swam awkwardly to the edge of the pit before hoisting herself up out. “Oof, sorry Celly, but I think Lulu's won the first act.” Dash side, not doing a very good job at hiding her smirk. “Alright, Lulu, next up is the trapeze!”

Lulu eagerly hopped forward, looking up at the ladder to the platform where the trapeze bar hung. She started her climb, her butt swaying back and forth and showing off to Celly who was waiting below. Lulu reached the top, grabbing the bars with her hooves as she glanced back down at the ponies below her. Her heart dropped into her stomach as she realized just how... high... she... was...

“Alright, Lulu! A swirly spiral!” Dash shouted up to her. Lulu nodded, and jumped off the platform. She swung through the air, but as she approached the second bar, the squeaky rubber of her exercise uniform suddenly slipped, and she lost her grip. She spun a couple times before landing in the net below the bars, bouncing up and down several times before coming to a rest, catching her breath.

“Tsk tsk tsk, that won't be any points for you Lulu. And such a shame after your last performance! You're up, Celly!”

Celly started her climb as Lulu did her best to try and climb free of the hammock like net. It was a lot harder than it should have been, and she was still struggling as Celly took her position above her.

“Celly?” Lulu called up. “Can you try not to fall off?”

“I wasn't exactly planning on jumping off,” Celly replied, a bit tartly.

“Okay, Celly, let's see how you do!” Dash instructed. “Do a swirly spiral!”

Celly pushed off from the platform, and began to spin through the air around her trapeze bar. It seemed that she was finding it much easier than Lulu did, and indeed easier than she'd found it on the balance beam… she held on easily, the lights at the top of the room glittering off the shiny material of her uniform and throwing highlights in all directions.

She went around and around, faster and slower, noticing in the back of her mind that she was going up and down again – slowing down as she went up, speeding up as she went down, so she felt like she spent more time sinking than she spent rising.

It made her feel all dizzy, giggly, but when Dash called for her to transition into a trapeze trance twirl she did it with flair – and a squeak-a-creak-a from her uniform as she flipped from one trapeze to the other, setting it swinging as she held on with her hind legs before transferring to her forelegs with another natural-seeming flip.

Lulu's eyes sparkled as she watched Celly effortlessly swing and swirl and spiral in the air, drawing her attention like a moving spiral or like a giant pendulum… making her yawn and blink, finding it harder than she expected to focus…

Celly's suit creaked as she spun and spun and spun, her eyes closing as she focused on the sensation of spinning, imagining she was sinking lower and lower, traveling down a slide ever deeper.

“Alrighty, now dismount!” Dash shouted up.

Celly let go of the bar without even opening her eyes, somersaulting several times before she landed on the opposite platform, striking a pose proudly. She opened her eyes, and stumbled back ever so slightly when she realized what she had just done. “Nice work, Celly! Top marks!” Dash said, trotting over to the next act. Lulu had finally managed to climb free of the hammock, Celly riding a slide down from the top of the platform and bouncing along on her butt when she reached the bottom.

They stepped up to the next act, two rings hanging from ribbons above an inflatable cushion. Lulu was ushered forward by Dash, climbing atop the cushy inflatable mattress. Her hooves sank into the material, causing her to sway and stumble as she wandered to the two rings. She wrapped her hooves around the rings, hoping she would be able to impress Dash with the next act again. “Now, show me a frilly filly flaunt!”

Lulu hoisted herself up into the air, lifting her her hind legs up carefully. She began to swing back and forth, showing off her diaper as she pulled the rings below her, doing a hoof-stand, shaking her butt left and right before dropping down and catching herself with her hind hooves, swinging forward and backwards on the ribbons.

Celly watched in amazement, wondering when Lulu had learned to do all these tricky moves, as her sister adjusted her grip slightly to make her sway left and right a little.

Admittedly, she wasn't sure when she got so good at the trapeze, but…

“Great start!” Dash praised. “But let's see if you can pull off a ribbon ring rave!”

Lulu paused for a moment upon hearing the words, then began what could only be a Ribbon Ring Rave – spinning around three times to twist up the ribbons, then letting them unspool and spinning her around faster. Her diaper stuck out a bit as she spun, and when she reached the end of the twirl she switched so she was using her hind legs to hold onto the rings and facing down towards the mattress below. Her horn was just above the inflatable material, and Celly held her breath as she wondered whether Lulu would pop it – but then the ribbons twisted up again, pulling her higher and raising a storm of crinkles as they compressed her big crinkly diaper in the ribbons and the rings.

It looked very impressive, but also very confusing… Celly could barely keep track of what Lulu was doing, let alone how she was doing it! But she didn't feel like trying, interested in just watching – and relaxing…

It was so easy to just watch Lulu spin around on the ribbons and the rings, alternately squeezed by the ribbons and rings and then dropping lower towards the mattress – until she flipped over to face back towards the ceiling, her crinkly rump now the thing closest to the mattress.

Rainbow Dash grinned widely as she watched Lulu perform, clearly quite proud with her stunts. “That's enough, Lulu, we have to give Celly a chance now! Dismount!” Lulu continued her spinning, the ribbons squeezing and squishing in on her tightly before she finally let go. She landed on top of the inflatable mattress, her diaper spiraling down into it from her momentum before it sprung her back up into the air. She waddled off, her eyes spinning as she seemed to suddenly realize just how dizzy she should have been. Celly took her place where Lulu had been, who was still stumbling around just a bit.

“The same as Lulu, Celly. Let's see a frilly filly flaunt!” Dash requested. Celly nodded, trying to hoist herself up with the rings. She immediately let out a squeak of surprise, finding even that part of the task to be difficult, let alone what else was required of her. She closed her eyes, puffing her cheeks out a bit as she lifted herself higher, Dash shaking her head a bit. “Really, Celly, you should lay off the sweets!” she said.

Celly tried her best, but eventually her hooves gave out and she flopped onto the mattress. She sank in further than she had expected, and with a cartoonish boing!, she was bounced up into the air. Her legs flailed instinctively, grabbing at the ribbons hanging beside her. Before she could come back down, her hind hooves had slipped through the rings, riding up to her flanks. The rings squeezed her diaper, and Celly fell back into the mattress before flying up again. She grabbed onto the ribbons, whimpering as she was bounced up and down.

Any questions Celly might have had about how she could even reach the mattress were lost in her general dizzy bouncing and confusion, feeling her diaper squished and squashed and squeaked by the rings and the mattress and the suit she was wearing.

She tried to hoist herself up out of them again, but that didn't seem to help – it simply unbalanced her, making her twist around and spin a few times, and the ribbons pressed closely in on her diaper as she got herself tied up in knots – each tangle tying her up more than the last, constraining her movement and in an odd way making it harder for her to think…

Celly found herself swaying gently back and forth, tied up in ribbons so thoroughly she had no clue how she could escape, and Rainbow Dash shook her head.

“Dear me, Celly!” she chuckled. “You're all wrapped up like a Hearthswarming present!”

The pegasus raised her soft hoof and poked Celly a couple of times, then did something and untangled her in a blur of rainbow light.

Celly found herself sat on the bouncy mattress, wobbling gently up and down, and shook her head a couple of times before the swirly blur of rainbow went gradually away.

“Now let's see how you do on the fourth and final gymnastics challenge!” Dash announced. “The balance balls!”

Celly and Lulu followed her once again to two small exercise balls, one a bright white and the other a deep blue to match Celly and Lulu's coats. “Up you go!” Dash commanded. Just as before, the two ponies trotted up to the awaiting performance piece, both of them placing their front hooves on the ball. “Just a simple bouncy balancing.” Celly jumped up onto the ball, her hooves sinking into the material with several creaks and squeaks of her suit. She balanced with ease, posing proudly. Lulu, on the other hoof, was wobbling back and forth atop her ball, her hooves stumbling around as she tried her best to stay on top of the ball. “See? It's just like the trampolines! Now a butt bounce!” Dash said, making a few marks on her clipboard.

Celly bent her legs, the ball bulging beneath her as she jumped into the air. She landed a few times on the ball before twisting a bit, landing on her padded rump. She giggled as her diaper squished the ball beneath her, and in turn squeezed her diaper. She was soon bouncing rhythmically up and down, looking over to Lulu.

Lulu didn't dare bounce, her balance was already so weak she was sure she was going to fall off of the ball any second. She glanced up to Celly, cheeks burning with embarrassment and jealously as she saw how easy Celly was bouncing, and just how much fun she looked like she was having. She tried to bounce, but only wobbled before flopping onto her ball, hooves spread wide. She squeezed the ball between her hooves just a bit... was it... bigger than it had been before?

“Um...” Lulu began, trying to draw attention to what she'd noticed, but the ball wobbled again – making it so she had to concentrate much more on not falling off, her hooves waving wildly and her suit squeaking aplenty.

Celly was having none of the same problem, bouncing on her rump before shifting her weight to bounce on her front hooves and waving her rump in the air.

“That's great, Celly!” Dash told her. “Just like that! Now let's mix it up a bit with a rump roll!”

Following the instructions, Celly began to run in place on the ball – making it so it began to slowly move about – and paused every few seconds to bounce butt-down and adjust her movement.

Each time she bounced, she went a little deeper into the ball – but she also sprang up higher than before, the ball itself getting just a little big bigger. Oddly enough, that didn't bother her… it just seemed like part of using the balance balls. After all, didn't it make the challenge slowly increase?

Lulu would have been quite happy for the challenge to not increase, and her attempt to do the same resulted in her ball wiggling backwards erratically as she tried her best to maintain her position on top of it. Her frantic hoof-wobbles were interrupted after a bit as she hit the wall of the gym rump-first, producing a bounce-off and a squeak-creak, a yelp of surprise and a loud booing-poing-oing as she bounced off her ball several times… leaving it much bigger than before.

Lulu whimpered as she wobbled, gripping the ball as it rolled forward, smothering her only to maintain its momentum and continue to roll, lifting her back on top of it. Celly bounced circles around her, flopping down into her ball and sinking almost completely into it. She gave it a tight squeeze as it distended before rebounding, sending her bouncing up into the air. Lulu looked up and had just enough time to let out a whine before Celly's ball came down top her, smothering her between the two rubbery surfaces. Celly's hooves wobbled as she had to adjust her balance a bit now that she was top two spheres. She peered over the edge, seeing Dash's encouraging smile below her, and grinning widely herself. She restarted her bouncing, letting herself sink deeper and deeper into the swollen material. The two balance balls inflated even further, muffling the helpless pleas of Lulu trapped between them. The swollen surfaces pressed tightly into her, squishing her muzzle and rubbing her diaper as they ballooned outwards.

Celly bounced higher... and higher... and higher! With each bounce she was practically swallowed whole by the overblown orbs, Dash quite happy with Celly's performance. Celly didn't even seem to notice Lulu's disappearance, too focused on the good feelings of vinyl and rubber squishing her, and how much fun it was to bounce!

She lost track of time a bit, bouncing and bouncing as Dash called out increasingly elaborate tricks for her to do – some of them with names so long she sort of got bored before the end, but which she could clearly do because she was able to pull off move after move!

Bounce, creak, squeak! Up and down, squished and released, the rhythms pulsed in her head and around her body… until something changed.

There was a ssssssss noise, echoing in the air, and for a moment Celly squeaked – wondering if that meant she'd gotten so confused that she'd managed to wet her diapers… until she realized she could feel something happening, and it wasn't that.

Instead, the air was slowly leaking out of the big bouncy ball she'd been balanced on… and leaking into her exercise suit, making it slowly puff up and inflate.

Celly lifted one hoof away from the ball, then another, trying to find where the leak was coming from, but it seemed just impossible to locate it as more and more air hissed into her suit from the ball and the unseen air leak.

Below her, Lulu found the same thing going on – only with bouncy balance balls on both sides, the air leaked into her suit faster than it was with her sister and her sports outfit was getting larger and larger faster and faster….

Dash continued to praise Celly as the two bouncy balls deflated, and before long Celly was wobbling atop a terribly inflated Lulu. The smaller alicorn's suit squeaked with every hoofstep from Celly atop her, who was having a bit more trouble maintaining her balance with her now bigger suit. “That wraps up our lessons for the day. Remember to stay bouncy, a fit princess is a good princess!” Dash said before turning to waddle off and leaving the two to return to the locker room. Lulu grunted a bit as Celly jumped off her, rolling her towards the door.

“Come on, Lulu! We're going to be late for our next class!” She said. Lulu tried to retort, but her quips were muffled by her own swollen suit as her head was smothered and she rolled along. Their progress was momentarily paused as Lulu became wedged in the doorway to the locker room, but several big shoves from Celly managed to squeeze he through, sending her bouncing off the wall.

“Celly! Stop rolling me around and find a way to get this thing off!” Lulu begged, wriggling her hooves uselessly.

Celly blinked, and, as if seeing Lulu for the first time, she gasped. “Oh goodness, I'm so sorry Lulu! I'll get you out, don't worry!” She scanned Lulu's outfit, trying to find a way to deflate it, all the while wobbling unsteadily as her own hooves had to be swung high into the air to compensate for how widely they were spread by her own air filled onesie.

“I don't know...” Celly said, after several long minutes of thought. “I just can't seem to think of anything we have which would let us deflate the suit. I can't find any sort of nozzle...”

“Come on,” Lulu groaned. “Really? Is there really nothing?”

“Nothing I can see,” Celly answered. “I'll look closer, though.”

She bent in further, inspecting Lulu's air-filled suit a bit at a time, wiggling as she moved herself clumsily sideways to look at the outfit a bit at a time.

Lulu wiggled. “Can't you do this any faster?”

“I'm doing the best I can,” Celly protested. “I think there might be something by your neck, though...”

She leaned in closer still, inspecting the astonishingly airtight material of the gym-class outfit to try and find the place it was supposed to be deflated-

BANG!

Both suits exploded at the same time, leaving Celly wide-eyed and staring and Lulu stumbling backwards before falling on her crinkly rump.

“What just happened?” Lulu demanded. “That was-”

“Pardon?” Celly asked. “I can't hear you!”

“What?” Lulu replied.

Celly reached a hoof up to try and get a scrap of pierced fabric off her horn. “I can't hear what you're saying, Lulu! Speak up!”

She managed to worry the fabric free of her horn and frowned, wondering why the suits had suddenly vanished, then stretched – enjoying the relative freedom of only wearing her school uniform. “Let's head to the next class, we'll be terribly late!”

“What?”

Celly simply rolled her eyes and took her sister by the hoof to lead her down the hallway. She rummaged around in her saddlebags to pull out the schedule. “Oh good, band's next, that's not too far away.” She said, tugging Lulu along behind her.

Lulu's hearing was slowly returning as she waddled along behind Celly, though she couldn't be entirely sure it was either. There was an odd... ringing still there. Though as Lulu thought about it, it didn't seem quite like ringing. It was a much fuller sound, one that reverberated through her head, and grew steadily louder both as her hearing returned, and the two approached the band room.

Celly and Lulu were too excited about getting to their class neither really thought about the fact that they didn't play an instrument. In fact, had Celly bothered to think about it, she didn't even think she had spent time in choir like Lulu had.

The odd droning continued to echo down the halls as the pair stepped up to the large double doors to the band room. They stepped inside, only to be met by a rather peculiar sight.

Another oddly too-puffy-appearing pink pony was standing on the conductor's podium, waving a baton around as she slowly swayed her rump left and right. What was more odd was the uniform she was wearing. It looked a little bit like a formal dress, if one stretched the definition of the word 'dress' as much as the material of the dress was. Bright and plaid, it hugged the conductor's form, and seemed to be at least partially the source of the odd sound echoing all around.

Celly raised her hoof. “Ah, er, excuse me?”

“Oh!” the pink pony performer said, smiling brightly. She stopped waving her baton around, but kept swaying her rump back and forth, and the droning sound continued unabated. “You're kinda late, but that's okay – we'll just have to do some recap!”

“I suppose so,” Lulu said. “I hope we haven't caused too much disruption?”

Neither she nor Celly were at all bothered by the total lack of other ponies in the class, the absence seeming simply unimportant.

“That's not a problem!” the teacher said. “By the way, my name's Pinkamena, but everypony calls me Teachy Pie! Or Pinkie, I guess, that works too, I'm a modern teacher.”

Celly frowned, then caught Pinkie's eye.

Cool, aqua, and definitely slit, it captivated her for an endless moment… and when she blinked and looked away, she didn't have any problems left at all with her teacher.

“So!” Pinkie said. “What kind of instrument do you girls play?”

“Well, ah… I'm afraid I don't know what would be best,” Celly said, feeling dizzy in general after her eye contact.

“Then I'll get you started on my yovidiaperphone!” Pinkie replied. “It's like a yovidaphone, but it's much better because you can wear it!”

“That's… quite a mouthful,” Lulu admitted.

“That's okay, you can just call it a bagpiaper if you want,” Pinkie said.

She jumped down from the podium, landing with a paarp-bounce on her rump, and the sudden blast of notes made both young alicorns stagger – feeling dizzy, for a reason neither could really place.

“Ooh, I know what colours would suit you!” she added. “Just a tick!”

Pinkie zipped away far more quickly than either pony would have thought possible, and returned just as fast. She was holding a deep purple mass of cloth in one hoof, and a crimson puffy bulge in the other. “Alright, get your instruments on so we can get practicing!” She said, dumping the instruments onto the respective pony.

Celly shook out her yovidiaperphone, trying to figure out which end was which. She eventually figured the more bulbous side must be the one around her rump, and a zipper running down its belly. She started to slip into the outfit as Lulu did the same, although she took a bit more interest in the line of pipes that ran down the back of the outfit not unlike the spines of a dragon. The seemed to lack any sort of holes, which only made Lulu wonder how Pinkie was expecting them to play any kind of complex piece of music with this. Those thoughts quickly faded away as Pinkie sat down again and let out a long drone of music. The two ponies were soon suited up in their yovidiaperphones, feeling the soft material hugging them comfortably.

“So... now what?” Lulu asked, looking herself over.

“Heehee, simple, silly! Just lift your rump up and-!” Pinkie dropped her butt to the ground, the pipes letting out a wheezy wail, and Pinkie giggling as she hugged her puffy plaid suit.

“That sounds...” Celly began, then her words slowed as she thought… it sounded something, but her first reaction seemed much less certain than she'd thought it was, and a moment later she couldn't even remember what her first reaction had been in the first place.

The music did sound nice, and she had to admit that she'd been meaning to learn an instrument one of these days…

Lulu was the first to give it a go, lifting her rump up a bit with the purple-black yovidiaperphone rising up with it – then she dropped her rump again, resulting in a wonderfully parpy sound which was deep and rich and nuanced.

“D-did I do that?” she asked, gasping. “I didn't know I could...”

“That's why a yovidiaperphone is such a great instrument!” Teachy Pie explained with a giggle. “Give it another go!”

Lulu raised her rump again and brought it down, producing a whole new symphonic-seeming sound which hung in the air and echoed around the room.

“You try!” Pinkie added, turning her attention to Celly, and the other sister lifted up her own bagpiaper with a wiggle.

“I'm not going to be as good,” she said, and Pinkie tutted.

“No, no, no!” she said, leaning closer with a smile – catching Celly's eye with her own again. “You've just got to believe you'll be good at it, and you will!”

Celly blinked, feeling woozy, and nodded – then she sat back heavily, landing with almost all her weight on her puffy instrument.

The blast of sound she produced wasn't quite so melodious as Lulu's, it was true, but it was louder and longer and just as compelling to listen to.

“That's right!” Pinkie giggled. “Now, let's try doing it to a beat!”

Celly dropped her rump to the floor to let out another loud wheeze, and she started to bounce in place. The beat wasn't quite exact, and her wheezes were much softer now that she wasn't putting her full weight behind each note. Still, she was building a slow rhythm, which quickly picked up in energy as she grew more comfortable with playing the instrument. She squeezed the pearl accented crimson yovidiaperphone, smiling as it blared out another set of notes. Lulu was swinging her rump left and right subconsciously as she listened to Celly play. She started to squeeze her legs together in time with Celly's bouncing, accentuating her sister's song with her own tune. Pinkie clapped her hooves happily, bouncing on her own butt to join in the melody as the students played.

“Now for something a bit more complex!” Pinkie said, hopping over to the chalkboard at the front of the room. She doodled up two ponies in respectively puffy yovidiaperphones bouncing their butts together. “If you combine your puffiness, the tune will be even more energetic! And the more energy in the song, the harder it is to think about anything else!”

Celly and Lulu stopped their playing just long enough to allow Celly to get back to her hooves. The two swung their rumps apart, only to swing them back and smack them together. They let out a loud 'paaaaarp!' as their butts collided, causing the two to giggle excitedly at the sound.

“Ooh, that looked great!” Pinkie cheered. “And it sounded even better! I bet you two could have a special sister rump bump spectacular!”

That sounded like a great idea to both Celly and Lulu, not that they could really focus on anything else in any great detail, and they put just as much energy into a second big dual-pony bagdiaper oomph-a.

Pinkie began bouncing on her own instrument again to give them a backing beat, then began to speak – not quite singing, but keeping her voice to the rhythm of the beat as the parp-tastic music pulsed through the room. “That's right! Keep it up! Now, let's try dynamic range!”

She giggled. “That means you put more force into the notes when you want more feeling! And the best way to do that is to not just bump, not just thump, but jump!”

Celly was the first to try that, copying her earlier opening move of putting all her weight onto the yovidiaperphone. The note which echoed out was louder, fuller, more insistent, and it did just as Pinkie suggested and made it even harder for either sister to think about anything but making the song sound just as good as it could be.

Lulu followed suit, this time actually jumping to land with the assistance of gravity, and if either Celly or Lulu had been trying to maintain a steady footing the musical pulse alone would have made their heads spin. But as it was it just made it easier to play more, louder, longer…

Celly and Lulu landed opposite each other to the beat of the song, Celly flying up into the air as Lulu came down with another loud parp! Pinkie bounced herself over the cabinet, rummaging around inside as the two played on. They jumped up, starting to parade around the room as they played, not paying much attention to Pinkie as she lifted her rump up and down in time to their bouncing and adding in her own accents to their tune every now and then. She eventually pulled herself out of the cupboard, holding several instruments in her hooves as she bounced back to the center of the room. “Keep going, girls! You're playing excellently! We're going to learn how accompaniment works now! After all, a yovidiaperphone is fun, but just think of how good you'll sound with all these other instruments drowning out...” The rest of Pinkie's words couldn't really be heard by the two fillies, with just how preoccupied they were with their playing. Their attention was finally diverted when a loud crash could be heard. Celly stopped, Lulu bouncing into her before turning to look to see Pinkie crashing a pair of cymbals together again, still bouncing up and down on her rump. “Come on, get a closer look!” She said over her own music.

Celly was the first to get moving again, able to approach while Lulu was still bouncing up and down from her landing. The white alicorn kept bouncing and playing almost unconsciously as she waddled closer, instrument swaying from side to side with every clash of the cymbals – until suddenly she was too close as Pinkie moved forwards with a giggle, and the cymbals clashed together on top of her.

Strangely she felt mostly a bit dizzy from the experience, popping back to her normal size after being briefly squashed – but had that really happened? It was such a strange experience that Celly decided to ignore it entirely, and giggle instead as Lulu got herself into almost exactly the same predicament with a parp-honk-crash.

“That's right!” Pinkie told them. “Feel the music move you – you don't need to think if you can just feel where it's taking you!”

She pulled out a set of extra-length horns, each for a different note, and Celly bounced down to land on one of them. Pinkie blew into that one, then the next one Celly landed on, and played her back and forth until she bounced off with the horn notes ringing in her ears and giggled, rolling backwards as the song reverberated through her head.

Lulu was inspecting a set of mutes, when she was suddenly bumped from behind by Celly. She fell into the shelves, the mutes falling down into the pipes on her Yovidiaperphone. The song from her pipes were muted slightly, and with each bounce, her instrument swelled. She squeezed her gut, blushing as it grew around her. She tried to reach around to her pipes, but her suit was too bloated to allow her to wrap her hooves around them. She whined as her suit wheezed, stilling swelling slowly bigger.

Pinkie bounded over, pushing a large chime down over Lulu's head, which was being slowly swallowed by her yovidiaperphone. Pinkie took a mallet and smacked it against the chime, causing it to ring and Lulu's body to quiver. Pinkie removed the chime, but Lulu continued to vibrate and shake, letting out a whine as her suit rumbled around her, the clear note of the chime echoing in her ears.

“Sounds like it's time for us to build up to a grand finish!” Pinkie said, clearing a space across the room with a sweep of her cushy pink rump. “Ready?”

Celly nodded, getting to her hooves, and was about to take a step forwards when Lulu landed on top of her.

“There we go!” Pinkie announced, and two big drums came crashing down from the ceiling. They landed either side of the two filly alicorns, and Pinkie jumped on top of one and then the other to hold them both in place at once.

“Drumroll, please!” she called, and – true to her word – began rolling the drums.

Celly staggered sideways into a drum and bounced off with a resonant boom, her yovidiaperphone unleashing an echoey parp as she did. That impelled her to bump into her sister, and her sister to bounce rump-first into the other drum with just as loud a parp and boom and just as big a bounce.

Bounce, boom, parp, bounce, boom, parp, the sisters picked up speed and bounced faster and faster as the drums rolled from the back of the room towards the stage at the front. There was a pair of cymbals there, ready and waiting, and they knew what was coming…

...and the drums rolled right up onto the stage bouncing the alicorns between them, as Pinkie jumped from the drums to trigger the cymbals. There was a mighty crash, and Celly and Lulu were sent wobbling out the door with their Yovidiaperphones trumpeting as they deflated – music flowing through them and making it almost impossible to think of anything else.

“Ta-ta!” Pinkie giggled. “See you! Remember your lesson! Don't forget that night is best!”