ponerpics.org · 7507989

Worktime: 24.04.2026 - 23.05.2026
Tier B Commission for "vandenbrand":https://www.furaffinity.net/user/vandenbrand

Story below made by "vandenbrand":https://www.furaffinity.net/user/vandenbrand

Thunderchief wasn’t really sure what she’d expected from an advertisement asking for volunteers to ‘test their capacity’, but… this wasn’t it.
The lab was cluttered; instruments, supplies, electronics, and some things she didn’t even really know what to call were stacked, piled, and tossed onto the tables and workbenches lining the wall of the sizable brick room she found herself in. To the owner of said room, a lithe white unicorn stallion who was busy picking through the clutter that took up most of a set of metal shelves in the far corner of the room, this was probably what he’d consider organized chaos. To Thud, it was just chaos.
While the stallion was finishing up his deep dive into his extensive assortment of stuff, an ever-growing collection of the things he was apparently looking for gathering in the emerald aura of his magical grasp, Thunderchief let her eyes wander around the room, her bored brain trying to pinpoint some of the things that she actually could recognize.
For one, there were a lot of gas tanks. A frankly unreasonable amount of gas tanks. Everything from medical oxygen bottles, to tanks of helium for party balloons, to industrial-sized cylinders of something called P-235 took up what little space along the walls wasn’t occupied by a table or shelf of some sort, clustered together without any real sense of reason.
The other thing that caught her eye was the whiteboard near a corner of the room taken up by a huge computer tower. On the board, in bright green marker, were the words ‘Capacity Testing (Limit Finding)’ above three categories; ‘Subject,’ ‘Volume,’ and ‘Diameter.’ The first category was simple, the column beneath it simply listing what looked like the names of other ponies. It was the other two that she couldn’t figure out. Volume and diameter of… what, exactly?
Her wings ruffled as she pondered the information on the whiteboard, racking her brain to try and figure out what the data was supposed to be. Some of those numbers were huge, numbers that, in her head, seemed to be the size of wagons, or even small buildings. Before she could think too much more on it, the unicorn stallion stepped away from the workbench and nodded.
"Alright, this should be just about everything we need! Sorry for the delay, miss...?"
"Oh, uhh... Thunderchief. Or Thud. Either works."
"Excellent. My name is Tai, and I'd like to thank you for volunteering here. Most of my previous volunteers have been ponies I know, and I've been interested in broadening the sample group." the stallion spoke with a chipper, but just a little clinical, tone. Thud's ears flicked at the way he seemed to emphasize the word 'broadening,' but she brushed past it. Tai did strike her as just a little... eccentric. Maybe it was a tic of his. Nodding, she continued.
"Sure, I understand. So... what exactly is the experiment you're running?"
“Yes, of course, we should cover that before we go any further. Tell me, do you have any experience with inflation?”
“...inflation? Wait, what… what do you mean? Inflating what?”
“Yourself.” Tai immediately replied, with such sincerity that it took Thud a long moment for his answer to click. Before she could offer up any other questions or protests, the stallion continued, “Your belly, specifically. That’s what I’ve been testing here. Your questions suggest that you’ve never done anything like this before, correct?”
“I-I don’t… yeah, n-no, I…”
“That’s perfect, actually.”
“R-Really?”
“Yes! I haven’t had a chance to experiment with someone completely new to being inflated! You see, from personal experience, I’ve found that ponies have this… latent flexibility. If you refer to my chart, here…” he trailed off, striding over to the whiteboard and lifting a marker with his magic, using it to point at the three columns of data. “...most of my other volunteers happened to be experienced with this, and they managed to hold quite substantial amounts of gas.”
“A-And this is… safe?”
“Of course! I’m curious, not cruel. Anything I do here, I’ve practiced on myself, at least once. My ultimate goal is actually to further the development of these." Tai explained, his horn igniting as he lifted a strange capsule of some sort off of one of the tables to his side, then brought it over to show Thud. One end was cylindrical, rounded at the end, and it seemed to be a cartridge of some sort. The other end, which said cartridge was fixed to, was much more mechanical, with a matte black body and a protruding mechanism, which ended in a particularly fine needle. "I've been trying to gather data to come up with proper dosage amounts for these. This is a dart which is designed to deliver a compressed gaseous payload from a distance, for both security and... recreation, you understand?"
"I... No, I... don't."
"It inflates things, ponies normally, to stop them or for their pleasure." Tai said with a sort of curtness, like he didn't enjoy simplifying his invention to such a degree. Thud's ears swiveled back, partly out of embarrassment, and partly out of dismay. This whole situation was beyond strange, and she was starting to feel like volunteering for this experiment might have been a mistake.
Though, despite its strangeness, she'd have been lying if she said that the idea didn't intrigue her at least a little bit. Variety is the spice of life, after all, and she was certain that Tai would treat her fairly if she decided she didn't want to partake anymore. Where was the harm in at least giving it a try? So many other ponies had tried it, based on the whiteboard's data, so who's to say she wouldn't get at least a little something out of it? Just as she was pushing the last of her doubts out of her mind, Tai spoke again, his voice back to its calm, collected self.
"So, would you like to go forward with the experiment?"
"Yes, I think I would."
“Excellent. What would you like to be inflated with?”
“I… I don’t know. Do you have, like… a recommendation, or…?”
“I’m glad you asked! For your first time, I think helium would be the best choice. It’s inert, it’s light, and believe it or not, most ponies say it actually feels very pleasant to be filled with. More so than something like air.”
“Alright, okay… so, uhh… how do you get it… in me?”
“I was just getting to that. Turn around, please.”
Before she could think too much about it, Thud obeyed, slowly turning in place. Just as her mind caught up and started questioning why she had to turn, Tai showed her. All at once, Tai’s magic began to shimmer, something prodded at the tight pucker of her tailhole, then whatever it was slipped into her ass until it came to a stop, some kind of flat base on the thing pushing into her with enough force to lift her hind hooves off of the floor for a moment. Her breath caught in her throat and she felt her face light up with blush, heat burning in her cheeks as her tail swiped downwards, flattening against her rump, covering her privates. As she processed the feeling of the strange object inside her, there was no mistaking what had happened, no question about it, though her mind wanted anything but to accept the fact.
He’d shoved a plug up her ass.
"W-What? I-"
"So sorry about the abruptness of that, but it's sort of a necessity. You don't want to leak, right?" Tai spoke with a tone that sounded professional and proper, but the smile on his face seemed just a little too enthusiastic. Thud floundered, at a loss for words, feeling the muscles of her butt clench tightly around the plug, holding it in, though that was more of a reflex than any conscious choice of hers. Glancing back, she found that a thin black hose trailed away from the base of the plug, and her eyes followed it across the floor, over to where Tai held the other end in his magic, and she watched as he made quick work of affixing it to the nozzle of a shockingly large grey tank. Just as she wondered whether or not Tai expected all of that tank's contents to fit inside her, the stallion nodded to himself, satisfied with the security of the hose, and he spun the valve on top of the tank open.
There was a hissing noise, followed immediately by a sudden pressure in her guts. She groaned, this new and unusual feeling inside her welling up, the sensation of filling in a way that she’d never even considered possible before sending confusing signals to her brain. The pressure worked its way through her, slow and steady enough that she could almost visualize it inside of her, the cloud of helium in her belly growing larger and larger. She started to pant, as though the fullness in her belly was already keeping her from breathing too deeply, though it was more likely a result of her minor panic over how quickly it felt like she was inflating.
After a minute of slow filling, the gas seemed to hit a wall and stop. It didn’t push any deeper into her, but the pressure didn’t stop climbing. She grunted and huffed, worried she’d already hit her limit, but before she could say anything, there was a long, low groan in her belly, and the pressure dropped. All at once, the gas had overcome whatever obstacle it had encountered, and she really began to fill.
She could feel her belly bulge downwards, rounding out into something resembling a baby bump, and her back arched downward with it, as though she had something dense and heavy filling her, though the helium was quite the opposite. She gasped involuntarily, the strange sensation of inflating so rapidly pushing some pleasant buttons in her mind, ones that she hadn’t even realized she had. What surprised her most was that it didn't hurt. There was a light, dull ache somewhere in her core, but really, it wasn't anything that brought her much concern. She felt her wings slowly unfold, and they hung limply half-opened at her side, as though trying to protect her bloated middle.
"You're doing great so far!" Tai cheered. He was sitting on the floor with the helium tank in front of himself, one forehoof on the valve, carefully monitoring how far it was opened. Thud only huffed in response, flashing a sidelong scowl at the unicorn. Tai's words weren't exactly as reassuring as he probably thought they were, at least not to her. It was hard to feel proud of something like this, having something stuffed up her butt and being blown up like some inflatable toy, but the more helium she took, the bigger she grew, and the tighter she felt her hide become... the better it was starting to feel. She wasn't sure how or why, but this bizarre situation and what she was feeling was starting to get to her, manifesting in a new ache in her body, a lusty, needy ache in her marehood. Her tail pressed a little tighter against her backside, a small, shameful part of her mind embarrassed over how turned on she was getting.
She needed to calm herself, and focus on something that wasn't how good being inflated felt. She shut her eyes, breathing slowly but shallowly, trying to clear her mind and let it stay blank. It mostly worked, her thoughts avoiding the situation at hoof for a bit, but it was a fight she was slowly losing. Every groan, every gurgle, and every creak of her growing belly caught her attention, and though she kept her eyes closed, she couldn't stop herself from picturing the swelling curve of her belly, wondering whether or not she looked as big as she felt, or if she was imagining the feeling of something firm and round beginning to brush against the insides of her hind legs. She'd just accepted it and started to let her mind focus on those pleasant thoughts when something inside her twisted, something in her guts kinked, and the dull ache of her swelling belly suddenly spiked into a sharp pain.
“Nnh! Ow, ow!” she hissed. Immediately, the flow of gas came to a complete stop, the hissing of the helium going silent. It was replaced by a soft shimmering sound, and an unusual warmth enveloped her underside. The pain eased back to its previous dullness as the soothing warmth worked into her belly like a massage, one that seemed to even affect the rest of her tense body, as she felt that same soothing warmth find its way into her haunches, her shoulders, and her neck. She let her head hang forward, reveling in this new sensation, stealing a glance at her belly once her head was low enough.
She was huge, her belly rounded out like a silver exercise ball hanging from her frame, larger than any mare had the right to be. It looked like she was pregnant with triplets, particularly large ones at that, and she was ready to pop. That last detail was especially true, as even with the pain she’d felt in her belly fading, the pressure inside of her wasn’t going anywhere. She would’ve loved to run her hoof across her belly and feel that tightness for herself, but with the way her legs trembled, she feared she might collapse if all four hooves weren’t firmly on the floor.
A bubble of emerald magic slowly drifted out of her, and the warm spot she’d been feeling came with it. That’s what it had been; Tai’s magic, soothing whatever kink had formed inside her, and seemingly going a step further, easing the strain that the rest of her body had been under. Speaking of the stallion, he quickly came alongside her, the glimmer of his magic fading away as he assessed her.
One of his forehooves came up to stroke her belly, and his gentle touch sent waves of pleasant shivers coursing through her, from the bottoms of her hooves to the tips of her ears. When his hoof pressed gently but firmly into the curve of her belly, as though he were gauging the tightness of her hide, her legs weakened, and for a moment, she feared she might collapse anyway. Thankfully, a small part of her brain (what little of it wasn’t awash with pleasure) reminded her that putting too much weight on her overblown belly probably wasn’t a good idea.
“Is that better?” Tai asked, his cockiness gone, replaced with a tender tone that suggested her sudden cry of pain had genuinely worried him. “Please, don’t push yourself, I don’t want to see you hurt. We can stop if you want, and-”
“N-No…” Thud panted, her heart suddenly racing. “M-More, I… I w-wanna keep going. Please…”
Tai smiled at her eagerness, but it wasn’t cocky or smug. It was genuine, the excitement he felt for this surprisingly capable rookie and his desire to help her find her true limit nearly overshadowing the pseudo-academic reason she was being inflated for. With a nod, he scooped the helium tank up in his magic, bringing it over to where he and Thunderchief stood, then cranked the valve open a couple of turns. Instantly, he saw the grey mare shudder with pleasure as her belly continued to fill, growing further and further away from the rest of her, and he sat beside her, using both forehooves to massage her impossibly taut belly, kneading the tightness out of her skin in an attempt to let her grow ever larger. She let her eyes close again, now reveling in the feeling of Tai's physical, not magical, touch on her belly. Dreamily, she let her thoughts dwell only in the moment, losing her sense of time to simply loving the attention she was receiving.
Suddenly, her belly brushed against something new. While it had been growing against the insides of her legs for a while, this was something else, cool and smooth, all the way down near her hooves. Her belly swelled against it, flattening, squishing, growing outwards instead of down. The growing cool patch on the warm skin of her belly made her shiver, but not from feeling cold. No, her shivering was accompanied by a strong wink of her marehood and a damp patch in her tail. Her mind had connected the dots, and it had driven her arousal into overdrive; her belly had reached the floor, and she still wasn’t at her limit.
It was an impossibly fantastic feeling, the way her weight kept her belly pinned, the flow of gas up her butt not changing in the slightest, and all that growth now went fully outward instead of down and out. Though she still doubted the ability of her belly to fully support her weight on its own, it seemed like she wouldn't have much of a choice in the matter soon, as the swell of her belly put more and more force on her legs, like it'd simply push them aside. Just as she thought that might happen, the weight on her belly... lessened. Slowly, it was reversing, like less and less force was pushing it downward.
Though her arousal had caused her wings to extend, they certainly weren’t flapping, so why did her hooves leave the floor, one after the other, until she felt the familiar sensation of floating? As a Pegasus, it wasn’t an unusual feeling for her, but here, she wasn’t working for it, with no effort from her wings at all. From that far corner of her mind that was still thinking, the answer came to her. It was simple; she was full of helium, and things that get full enough with helium tend to float.
“We have liftoff!” Tai’s sudden cheer all but confirmed it. Somehow, despite her inexperience, she’d managed to hold enough helium in her guts to float on her own. Just like… a big, silvery, party balloon. That thought had just crossed her mind when something slipped around the pastern of one of her hind legs, then tightened snugly around it. After another moment of ascension, she came to a sudden, but gentle stop. Tai’s voice came again, “There. Don’t want you floating away, right? Not when you’re in the home stretch!”
That’s what that feeling had been. Tai had tethered her down, a string or rope of some sort tied around her leg. She really was just a big Pegasus party balloon…
…and that thought drove her wild.
More and more, bigger and bigger, tighter and tighter. Every second she spent filling was one second more than she thought would ever be possible, her limits pushed to an extreme that she never could've imagined. She wished it would never end, that she might blow up to the size of a hot air balloon, or a blimp, or something even bigger, and she'd stay that way for as long as she could. What she couldn't have heard over the sounds her body was making, the creaks and groans of an overfilled balloon, was that the hiss of the flowing helium had begun to taper off, fading to complete silence after a long few minutes.
“Oh my, I think you may have just emptied the tank!” Tai announced with pride, eyeing the gauge on the top of the tank. His smile widened at what he found, and he beamed up at the inflated mare. “You really did take the whole thing! That’s 4.5 cubic meters! Are you sure you haven’t inflated before? I'm impressed!”
Thunderchief didn’t respond. In fact, she’d hardly heard Tai’s praise from below her. Her mind was positively aglow with lust, so lost in the fogginess of her arousal that she hardly could remember why exactly she’d been filled to bursting with helium, much less fathomed her accomplishment and the numbers associated with it. It did register with her that the helium had stopped and she was no longer growing, but then and there, all she had the focus enough to do was what she’d been doing since she took flight, massaging her massive belly and coaxing every little bit of pleasure she could out of it, savoring the jolts of pleasure that ran up her spine with each gentle squish and squeeze.
A cool band very gently tightened around her middle, passing directly over her brand new outie of a belly button, sending new waves of pleasant shivers running through her. Her hazy mind vaguely registered the measuring tape that drifted up past her eyes when that cool band stopped squeezing her, and her ears flicked when Tai hummed enthusiastically from below her.
“Your belly measures about 2.1 meters around, give or take a bit due to your… squishiness. Right where you should be, based on the simple math of it. You did fantastic for your first time! How do you feel?”
Once again, the inflated mare didn't respond, though f