Happy Accidents

by Wandering Pigeon

Rating: mature
Tags: Derpy Hooves, Sex, Random, My Little Pony: Friendship is Magic, Nightmare Moon, Porn, Fetish
Length: 4373

Derpy is Nightmare Moon's caretaker. This will end well.

Depowered, but not destroyed. Nightmare Moon clings to life, even if life for her now means being restrained in Celestia's dungeon and stuck in some regrettable fashion choices. But at least she can pass the time by tormenting the ponies her sister sends down to care for her. Or do... other things with them.

Warning: diapers, diaper usage, ABDL themes, sexual themes.

Published 2020-04-18 23:00:01 UTC
Last updated 2020-04-18 23:00:01 UTC

Just Don't Know What Went Right

Pure, unbridled rage.

Nightmare Moon had never been so furious in her entire life, and she was a being born out of such emotions. Her grand plan, her return after a millenia wasting away on a barren rock, thwarted before it had even begun. Six noponies had somehow gotten together the Elements of Harmony. Mere hours after her glorious return, a rainbow bridge of light put an end to it all.

But not to her.

To the surprise of everypony, Nightmare Moon had not been vanquished. Defeated? Certainly. Depowered? Regrettably. But deleted? Not even close.

It had been one small victory amidst the jaws of defeat, seeing Princess Celestia break down and cry upon realizing her precious sister had not been restored. Nightmare would savor that look, those glorious sounds, for centuries to come. But relishing in it would have to wait, given where she’d found herself.

Stripped of everything, she’d been unable to flee. The Princess’s guards had quietly taken her into custody while the monarch consoled her citizens with the knowledge that the eternal night had ended rather abruptly.

She’d been on the first train to Canterlot, as a prisoner, not a conqueror. But through the kindess of her heart, or maybe just desperation, Celestia granted Nightmare stay in the room meant for Luna upon her return. Out of spite, Nightmare had destroyed every little thing in that room. Bedsheets, old mementos, wallpaper, furniture… even hoofcuffed she proved herself to be quite destructive.

So they’d hauled her out cackling and gloating, finally moving her to an actual dungeon. But Nightmare wasn’t satisfied until her sister’s worthless soldiers considered her a real threat. Fangs gnashing, hoofs stomping, horn sharpened and stab-happy, she’d sent three of them to the hospital before they finally started to take her seriously.

And the only downside was, they decided to take her seriously.

Deemed to dangerous to let out, even for something as minor as using the restroom, her sister found a… creative way to declaw the wild cat in cell one.

Nightmare struggled, kicking her hind legs while pushing her forelegs struggled to move at all. For the umpteenth time she tried to roll off her back, and for the umpteenth time she failed. An infuriating crinkling sound filled her ears, and she wanted to scream.

Pure, unbridled rage.

Nightmare was smack on her back, hind hooves bound by heavy ropes pulled taut at either end of the wall. They kept her legs suspended in mid-air, barely able to move. But that wasn’t the only thing that kept her gait spread.

They really were set on not letting her out, even for the restroom. And when one guard found her bedpan bucked into his face, they’d settled on plan B: a diaper.

A diaper.

They’d put the Mistress of Night in a diaper!

Just thinking about it made Nightmare want to scream. An insulting poofy diaper, lined with layer after layer of padding, swallowed her pelvis. It was so large that her flank no longer touched the ground, despite how much it sank into the soft material. Any little shift in her weight would start a chain reaction of crinkles that would make the guards outside her cell snicker just loud enough for her to hear.

Curse that sun-loving witch! Nightmare seethed internally. The smug look on her face when she’d first displayed one of these to Nightmare had said it all. This was her revenge, in a way, on Nightmare for failing to turn back into Luna. The way she casually remarked it would be a “humbling” experience for her was just the muddy icing on the dirt cake.

That hadn’t even been the end of it, either. It seemed like Nightmare’s initial flustered look had emboldened the Sun Princess. She’d went and themed Nightmare’s entire punishment around a foalish theme. Aside from the diaper, a special onesie also adorned the dark alicorn. Pale blue, and made of snug cotton, there was no way it wasn’t meant to invoke Luna’s memory to her constantly. It hugged her body tightly, save the diaper. The flap of fabric meant to cover her butt couldn’t quite fit over the glorified cloud on her plot, and so hung open.

The arms of the onesie were particularly unique. Sewn back into the body, the forced Nightmare’s fore legs up against her chest, like a straight jacket. A cotton posture color ran the length of her neck, culminating in straps that looped around her snout and over her head. For good measure, they’d included an inhibitor ring or two or ten around her horn. Just because she’d lost her magic now didn’t mean these ponies were taking any chances.

Nightmare tried to sit up, rolling on her padded behind and wincing. No dice. She let her head flop down, hitting the silk pillow below her and sinking in. Some would say that little cushion was a kindness still afforded to Nightmare, but it only served to enrage her further. How dare Celestia think she can get away with showing her kindness? After everything else she’d put her through? The rightful queen of Equestria was stuck below her castle, bound and diapered. Was she really forced to sink even lower and accept the good graces of her captor?

She snorted, nostril’s flaring. Ancient curses sprung to mind, but she bit back all of them. She’d learned not to make noise at the point. As if she wanted to give the guards a reason to come in, snatch the pacifier hanging from the wall, and lock it in her mouth again.

So Nightmare remained silent, staring up at the ceiling as she contemplated revenge. Glow in the dark stickers, dozens of stars and a crescent moon, stared back at her. It made her groan in the back of her throat. Just another foalish touch, courtesy of Celestia. But it did fuel those revenge fantasies of hers.

When I get out of here, I shall lock her in a crib two sizes too small, have her fill up a hundred accursed diapers, and then banish her to the sun! Most of Nightmare’s revenge fantasies ended with “and then banish her to the sun”. She couldn’t help it.

But, they were only fantasies. Right now, Celestia’s oh-so precious student was currently working out a way to have the Elements reform her for real. And with security so tight on Nightmare, and her own magic drained and gone, she had no way of escape until they finally found a way to turn her.

How long has it been now? Nightmare wondered. How many days had she spent in this cellar? How many times had she been reduced to… she shuddered… to using the diapers Celestia forced on her? Too many times, that was for sure.

She tried to pull her legs together and snap the ropes that held them. Padding surged into her marehood, pushed in by her squeezing thighs. Nightmare blushed, barely keeping back a “Guh!” of surprise, and relaxed her legs. Nope. She was never doing that again.

Her stomach rumbled, her last meal but a distant memory to it. She frowned at the thought, wing tips curling. It was almost mealtime… and that meant it was almost time for Celestia’s true torment.

“Heya Bronze Shield! Steel Courage!”

The guards whose names Nightmare had already forgotten grunted their hellos. Keys jingled, and the door to Nightmare’s cell opened as her caretaker strolled in.

“Hiya, Nightie!” The pegasus-shaped thorn in Nightmare’s side chirped. “Did ya miss me?”

Nightmare hissed.

Derpy Hooves smiled undaunted, her mismatched eyes as cheery as ever as she slung her saddlebags full of supplies off.

This mare. This… creature was the true curse of Nightmare’s imprisonment. She thought it couldn’t get worse than the diapers. There was no way it physically could have gotten worse. But in her sister’s quest to find a caretaker for Nightmare that wasn’t scared of her, she uncovered this pony.

“I made my special secret banana muffins today!” Derpy exclaimed, pulling out a plastic tub of her newest concoction. She leaned in close and whispered into Nightmare’s ear, “the secret ingredient is extra banana.”

“I will eat your heart,” Nightmare growled.

“Boy, you sound hungry!” Ever optimistic, or maybe just oblivious, the mare who’d earned the official title “Royal Foalsitter” sat down next to Nightmare’s head to feed her. “Who’s a hungie girl?”

“Nopony will never find your body.”

Derpy just smiled. “Well, I was always good at hide and go seek.”

Nightmare screamed internally. She screamed for a very long time.

Derpy scooted forward, lifting Nightmare’s neck up in order to set the alicorn’s head in her lap. She pulled a muffin from the container and pushed it towards Nightmare’s mouth. Her lips stayed closed.

“Aww, c’mon now, Nightie.” Derpy frowned. “Here, open up for the choo choo train!”

“Mm-mm,” Nightmare shook her head, mouth a thin line.

Derpy started bouncing the muffin towards her face. “Chugga chugga chugga chugga…” she pushed it against Nightmare’s lips. “Choo choo!” She backed up the muffin train, and started over.

“Chugga chugga chugga… choo choo!”

Crumbs were starting to pile up on Nightmare’s lips.

“Chugga chugga chugga chugga… Choo! Choo!”

The muffin was getting squished. Nightmare just glared.

“Chugga chugga chugga chugga chugga chugga chugga…”

“Alright already!” Nightmare shouted. She let her jaw hang open, saliva dripping from her fangs. She hoped to take a bite of Derpy’s hoof with her at least.

“Choo choo!”

“Mmf!”

The muffin filled Nightmare’s mouth too well. She was forced to chew on just it, the cinnamon, banana confection dancing across her taste buds as she did. How dare this pony be a good cook on top of being so annoying!

“Next one!” Derpy retrieved muffin number two, Nightmare still not ready to swallow. “Chugga chugga chugga…”

They continued on like that until Nightmare had choked down the last of her lunch. Derpy’s high pitched “choo choos” never taking it easy on the alicorn’s ears. She kept them folded down throughout the entire feeding, hoping Derpy would catch on. But she never did.

Finally, mouth dry and caked in crumbs, she swallowed her last chunk of muffin. Nightmare gasped for air as Derpy set her head back down on the pillow. It was almost over.

“Hehe,” Derpy giggled. “You’re a messy eater, Nightie.”

“And you’re an idiot!”

Derpy pulled a napkin from her saddlebag, licked it, and began wiping off the smattering of crumbs around Nightmare’s lips. The incarnate of evil could only blush as she was treated like a little filly by a mare she dwarfed in years. “Stoppit!”

“No!” Derpy stuck out her tongue playfully, and smeared the napkin across Nightmare’s face. “Cause you’re too cute when you’re mad.”

Now that blush spread, dominating Nightmare’s cheeks. “I am not cute!” she hissed.

Derpy just shrugged. “Suit yourself, cutie. You know, if you’re going to keep eating like a foal, maybe I should talk to your Mommy about getting you a bib.”

“Celestia is not my Mommy—er, mother!” Nightmare kicked her legs, diaper crinkling noisily. “And I don’t need a bib!”

“Hmmm… I think I’ll ask your Mommy anyway. Just to be safe.” Derpy retreated to her saddlebags before Nightmare could fire back.

“Grr!” The mare shook her hind legs again, trying to shake off her directionless fury. For some odd reason, she couldn’t get the blush off her cheeks. Something that hadn’t happened since her first few days in diapers.

How could one mare be so infuriating? She pondered. Truly her sister had changed her mind on the subject of torture these past few centuries.

“Okay, baba time!” Derpy was back. Hooray.

“No!” Nightmare turned her head away from the mare in a huff.

“Aww, come on. Don’t be fussy now.” Derpy poked at Nightmare’s cheek with the amber nipple of a foal bottle.

“I’m not drinking out of that again.”

“You always say that Nightie…”

“And I always mean it! I know Celestia has been putting laxatives in those things and I won’t stand for it anymore!”

“…You know, I bet some nice, cool milk will wash away all those muffin bits between your teeth.”

Nightmare whirled back around. “There isn’t any muffin between my—Mmmph!” Derpy shoved the bottle between Nightmare’s open lips.

She’d been deceived. Never in a million years had she expected this mare to do something clever.

She couldn’t even spit it out. Derpy slipped straps around the neck of the bottle, keeping it stuck in Nightmare’s maw. The only way to get her mouth back was by finishing every last drop.

So, even though she let it hang in her mouth for a moment, she eventually deigned to suckle.

Cold and creamy milk came out. First in a trickle. Nightmare was left with tantalizingly little milk until she decided she wanted more, suckling even harder on her baba for force more out. It splashed down her throat like a waterfall, and soon she was gulping and suckling like a champ.

“Aww,” Derpy cooed. She took a seat next to Nightmare, and began stroking the ethereal mane that wisped by. Despite protest grunts, of course. “I know you don’t like being called cute,” Derpy murmured. “But I think you’re very pretty.”

Nightmare almost choked on her milk. “Grrph?!” Where had that come from? And why was her blush getting hotter?

“I’ve never seen a mane like yours before.” Derpy ran a hoof through it, gingerly. “Even the Princess doesn’t have something quite like this.

“Hmmph.” Nightmare suckled with an odd sense of pride. At least this idiot could recognize a quality mane when she saw it. …Half saw it.

Derpy’s mismatched eyes sparkled as she brushed Nightmare’s mane. She let the compliment hang in the air for a moment. Silence, save suckles and crinkles.

“Has anyone ever told you you’re pretty before?” Derpy asked.

Nightmare growled to let the mare know she was pushing it.

“I like to think I’m the first.” Derpy smiled. “But that’s also kind of sad. Maybe you’d be nicer if more ponies told you how beautiful you were.”

Nightmare was floored. Absolutely, and completely. Derpy actually knew Nightmare was being mean to her? She’d never been so shocked.

She shifted in her position, unnerved at Derpy’s sudden compliments on top of that. It was making it harder and harder to fight back the redness at her cheeks. She was not going to stand for her pristine coat to be sullied like this by the words of a commoner.

“Grrff ffrrph!” Nightmare batted at Derpy’s side with her horn, finally pushing the mare away.

“Golly, you sure are grumpy today,” Derpy smirked, her eyes half-lidded. “Did somepony go potty?”

“Wrrfff?!” Nightmare struggled to sit up and smack the mare.

Derpy’s wings ruffled nonchalantly. “Well, it’s just you only get like this when you’ve got some poopy in your pampers.”

Nightmare’s face was pink. “Shhherr rrrupp!” She flailed, her diaper crinkling noisily as she did. She didn't even need to go.

...Much...

“Let me just go check on that.” Derpy waltzed down to Nighmare’s waist, ducking under one of the ropes to be eye to padding with the world’s largest diaper.

“Mmm mm!” Nightmare attempted to buck the mare’s head off, and failed. She really wasn’t doing much right now besides suckling, around half her bottle’s milk now in her stomach.

“Let’s see here.” Derpy’s hoof grazed the padding. Layer’s crinkled together, and Nightmare felt the gentlest of pressure on her inner thigh.

She huffed. Unable to do much more between her muffled complaints and failed murder attempts, Nightmare relaxed a little. She focused instead on wiping away her blush and drinking the milk that poured from the rubber nipple between her lips. At least Derpy wasn’t fiddling too deeply with the diaper. Once she realized Nightmare was clean she’d stop teasing her and move on.

“Well, looks like you’re still clean. Guess we can—Ah!”

Nightmare couldn’t see it too well from her angle, but she felt it. Derpy slipping on the onesie flap, her body tumbling and twisting, her face diving straight into Nightmare’s padded crotch.

The mare’s features imprinted on the padding, pressing deeply into it. Crinkling loudly, it compressed, squeezing out a puff of foal powder and filling the room with the infantile scent.

Her marehood never stood a chance.

“MMMPH!” Nightmare bit down on the amber nipple. Her wings laying flat on the floor suddenly sprung to attention, stiffer than they’d been in a millenia.

It was like a warm hug, in the best possible place. Padding nestled into Nightmare’s privates, forcing a second cry of lust from the alicorn.

“GMMMPH!” Her neck arched back. Her blush stained her cheeks. Though the padding’s light touch had always teased her, this was a sensation Nightmare had never dreamed of before.

And she got a mere second to revel in the heavenly feel, before the awkwardness set in.

Stars above… don’t tell me she heard…

No, there was no way she didn’t. Nightmare’s muffled moans hung in the air as Derpy froze, face still swaddled with padding. Neither of them moved, or breathed. Nightmare’s automatic suckling had even stopped, though the hole her fangs had punctured ensured her cheeks stayed full of milk.

The awkward silence filled the room. It wasn’t until a new sound entered that they could reset. The clink of armors as the guards ended their shift, none the wiser of what had just occurred inside. And it seemed the relievers were a little late, as no hoofsteps came to fill the emptiness outside.

Derpy pulled her face out of Nightmare’s crotch, slowly. She probably meant to be considerate, but every single movement of padding sent jolt’s through the alicorn’s system. Taking her time like that was almost cruel.

A red pegasus poked her head up over Nightmare’s diaper. “S-Sorry…”

Air hissed as Nightmare’s diaper took back its old shape. Nightmare was breathing heavily through her nose, gulping down milk as her bottle finally emptied.

“Yrrff… phrr…” Her eyes rolled back in her head, the diaper’s unrelenting touch driving her mad. Her libido hadn’t had this kind of stimulation in over one thousand years. She was so desperate she was getting off to a diaper.

And she loved it. Even a wall-eyed mare could see that.

Derpy’s ears pricked up, even as her blush deepened. “O-Oh?” Her expression shifted to a grin that was almost… sadistic. “Did you like that, Nightie?”

“Mmmrrr…” Nightmare couldn’t escape the hint of pleasure in her response. Her marehood twitched at the memory of the puffy pressure. What she wouldn’t give to—

CRINKLE

“MMMF!” Nightmare head lifted off her pillow. Eye bulging, she saw a half-lidded Derpy pushing her hoof deep into her padded crotch. “MMRRPH!”

“I thought you did.” Derpy’s wry smile grew. She drew a circle into the layers of the padding with her hoof. Then giggled at Nightmare’s pleading moan. “And here I thought you didn’t like your diapees.”

“Mrrf!” Nightmare managed a spit of anger behind that moan, nearly choking on formula in the process. At least she’d finally polished off the bottle.

Derpy giggled again, pulling her hoof away. Nightmare’s marehood winked as the padding lifted off. She tossed her head back down, writhing against her restraints. She was horny. She was horny and she hated it.

“Aww, is somefilly getting all frustrated?” Derpy teased.

No! Nightmare screamed internally. But her hooves curled anyway and Derpy laughed.

“Well…” Suddenly another hoof jumped into the padding. And another. Nightmare caught herself moaning into the padding. “...I think that’s a good thing.”

Derpy was climbing on top of Nightmare, free soloing the massive diaper and pushing the captive alicorn even closer to the edge. She reached the belly summit, sliding down the other way to boop her nose into Nightmare’s. “Don’t you?”

The pegasus was still blushing, almost as badly as Nightmare was. But she maintained her control of the situation, pushing a hind hoof down on the diaper behind her. Another moan.

“Hehe!” Derpy’s wings flared. “I’ll take that as a yes!”

“Mmmm…” Nightmare’s eyes were rolling in the back of her head. Derpy’s hind hoof was clumsy as it bounced against the padding. Her diaper pushed in, and relaxed. Pushed in, and relaxed. Her poor marehood was wet after just a few cycles of this. All the while Derpy just stared (or at least, attempted to) longingly into Nightmare’s eyes.

“I’ve been wondering what it would be like…” She whispered. “To be with somepony so pretty.”

Nightmare grunted and moaned. She wasn’t paying attention to Derpy at all. But she started to when the pegasus unwrapped the straps around her muzzle and let the bottle drop to the floor.

“Y-YooOOUUUuu!” Another push into the padding. Nightmare couldn’t contain herself. She was soooo desperately close.

“I can’t believe it happened by accident too…” Derpy murmured. And then she kissed her.

Nightmare should have bit the mare’s tongue off. She should have… She…

She closed her eyes, and leaned into it. Her body felt hot, her wings stiff. Derpy was soft, and the diaper was softer. Both were pressing into her, and she couldn’t control the feelings they brought.

Derpy dug her hoof in even deeper, and Nightmare felt her marehood twitch. She was almost there.

Her tongue wrestled back against Derpy’s. Her forelegs struggled against her binds, trying and failing to wrap around her partner. Derpy locked her own around Nightmare’s long neck instead. A number of wet smacks of their lips joined the crinkling sounds the fill the room. Thank the stars there weren’t any guards at the moment.

Nightmare was so worked up, she didn’t feel the rising pressure in her bowels until it was too late. A noisy fart cut through the cell, shattering the mood as quickly as it came. Derpy’s mouth broke away from Nightmare’s. The alicorn groaned, unable to stop it.

She filled her diaper.

Hot, steamy mush collapsed into the padding. Forced out so suddenly and violently, that it was fair to call it an explosion. Her massive diaper swelled to even greater sizes as warm goo punched against the pillowy walls.

Derpy slowly turned to look, catching a glimpse of the browning padding. Her nose wrinkled as the smell hit. Her snout scrunched. “Ugh…”

Nightmare didn’t have the luxury to be grossed out. She was used to the feeling, the smell by now. And the shame of that somehow dwarfed how horny she’d felt. Still felt, actually.

Despite the filling diaper, her marehood didn’t seem to mind. Even as the sensible part of Nightmare’s mind returned, her libido held firm. Her ballooning diaper, and the warm mush within coating her backside, didn’t make her any less desperate for release.

“Unf!” she bit her lip. Hind legs kicked against their ropes. They elicited squishy crinkles, but failed to satisfy her urges. Urges that were still mounting.

“Change me at once!” The moment of passion she’d allowed herself to be caught up in was definitely over. Even if her face was still pink. Her marehood twitched under the messy padding. “Grrrgh!”

“Phew!” Derpy waved her hoof. “That’s a big one.”

“I told you my sister is spiking my milk with laxatives!” Nightmare insisted. Anything to throw the blame of her accident elsewhere. She twitched again. Her marehood wasn’t calming down! “Change me!”

Derpy rolled off Nightmare’s body, wobbling to her hooves as though she were dizzy. “Mmm…” She touched her lips, no doubt still buzzing from the kiss. Nightmare’s sure was.

“I said change me!” She demanded again. She couldn’t ignore how horny she was getting, but she couldn’t do anything about it either. She just wanted out of her messy diaper before it started to feel like she was enjoying it.

“Hmm…” A sultry look back at the prisoner. “I don’t know, Nightie. You really killed the mood there.”

“Derpy, I am warning you!”

“And I was just starting to enjoy myself.”

“Derpy!” The pegasus swatted her on the nose. “HEY!”

“Ask nicely,” Derpy insisted. “It’s not my fault you made a stinky. Unless I’m that good of a kisser.”

“You were adequate at best!” Nightmare kicked, and flinched as the squishy sensation that caused.

“Aww, Nightie. You know you loved it.” She kissed the rightful Queen of Equestria on the cheek. “But since you’re being fussy, maybe you can wait until dinner time for a change.”

Nightmare’s eyes widened in genuine fear. Derpy had never refused to change her before. And now of all times to… Her tingling marehood made her tense up. “N-Now don’t be hasty here…”

The shuffling of armor outside. The new guards were at their posts.

“Dinnertime, I promise.” Derpy winked. “And maybe we could pick up where we left off then.”

Yes! “You…!” She bit her lip. Any movement now jostled her diaper.

Derpy already had her supplies in hoof, and was moving to the door.

“NO!” Nightmare commanded. “Get back here and change my diaper!” The door was open. The guards would hear, snicker, but she didn’t care. “Do not leave me like this, you whelp!”

“Bye-bye, Nightie.” Derpy blew a condescending kiss to her captive, and the door was shut.

And Nightmare was left alone, a mudslide in her diaper, and an unsatisfied marehood that wouldn’t release.

“Derpy!” Nightmare kicked furiously! “Derpy get back here!” Her mess sloshed around in her diaper. She didn’t care. “Derp—” And all of a sudden, the right mixture of padding, mush, and movement did the trick. Nightmare’s marehood flared, the numbing heat of an orgasm filling her body.

“Derrrrrrppppyyyy~”

Pure, unbridled bliss.

Her head tilted back, eyes squeezing shut. She’d finally climaxed, in a soiled diaper no less. And that meant all she would have to keep herself company for the next few hours would be dirty padding, and thoughts of that stupid, gray pegasus.

But for now, Nightmare just bit her lip, and tried to enjoy her first orgasm in over a thousand years.

...Maybe it wouldn’t hurt if those brats take their time with the Elements...

Author's Note

WP rises from his lair.

"Nightmare Moon X Derpy diaper slash fic!"

And he disappears back into his slumber.