Little Sister, Big Troubles [Commission]

by Midnight Shadows

Rating: mature
Tags: Rarity, Sweetie Belle, Slice of Life, My Little Pony: Friendship is Magic, Fetish
Length: 6652

When Sweetie Belle and Rarity are left home alone while their parents go on vacation, arguments and shenanigans ensue that result in a padded outcome.

Warning, Contains diapers and mild diaper usage, you've been warned.

Commissioned for anonymous.

For the full formatted version please use the google document located Here

When Sweetie Belle and Rarity are left home alone while their parents go on vacation, arguments and shenanigans ensue that result in a padded outcome.

Published 2020-01-21 10:00:01 UTC
Last updated 2020-01-21 10:00:01 UTC

Little Sister, Big Troubles

‘Little Sister, Big Trouble’

Written By:
Snow Blitz
Midnight Shadows

“Now remember, keep an eye on each other, don’t burn the house down, no magic that you don’t know what it does, and absolutely no colts!” Cookie Crumble said as she pushed several suitcases out the front door to her home. “No fighting, I expect you two to get along while we’re gone.”

Sweetie Belle and Rarity glanced to each other before looking back at their mother with not so convincing smiles, already on each others nerves. “We’ll be fine Mother, enjoy your trip.” Rarity stated, ushering the mare out the door.

“And don’t forget-”

“Okay bye love you Mom!” Sweetie Belle exclaimed, her horn illuminated, levitating the rest of her parents luggage through the door.

As the two older ponies entered the waiting wagon outside, the mare yelled back. “And remember, Sweetie Belle is in charge after last time!” She exclaimed with a teasing voice before the wagon pulled away.

After a few moments Rarity turned to her younger sister, glancing down at her. “You do know Mother was joking.” She paused. “We’ll be fine as long as you don’t cook anything.”

“Mom said I was in charge.” Sweetie Belle said glaring at her older sister. “That means you have to listen to me, not the other way around.” She paused thinking about the cooking comment, “I can cook now! I’m not a little filly anymore.”

“Well you may not be a little filly anymore but you’re still my little sister, and still a filly at that.” The older mare announced. “Now why don’t you run along and play?” She stated flippantly, turning towards her bedroom. “Oh and don’t forget to wear your diaper to bed tonight, I don’t intend on doing any laundry.”

Sweetie Belle felt her cheeks reddening, “It’s a pull- I mean it’s not a diaper! It’s my special protection, and I’m not a foal.” She half shouted up the hallway, stamping her hoof in a show of foalish frustration.

Rarity stopped just outside of her room, still facing away from the filly. “Perhaps, but it’s still made by a diaper company; with cute little prints and wetness indicators for a little unicorn filly who’s still acting like a foal.” She stated before entering her room and closing the door, leaving Sweetie standing alone in the hallway.

“If she thinks I’m the foal, she’s wrong. I’ll show her!” Sweetie grumbled to herself, she walked down the hall to her own bedroom, at first she thought about slamming the door but ultimately decided against it. “We’ll see who the real foal is!” Once she was safely alone in her bedroom the filly began scheming, she had her plan all mapped out. After bedtime she’d sneak into Rarity’s room and pull the hoof in warm water trick, making her sister wet the bed. “It’s a genius plan Snuggles, you can’t tell me otherwise.” She said aloud to her favorite plushie.

Later that evening, Sweetie Belle was busy playing as she noticed the time. ‘I’d better put on one of those stupid things.’ She thought to herself as she opened up her dresser, an entire drawer devoted to her nighttime problem. Her horn light up, pulling items out, as soon as her protection, rash prevention cream, and powder were all levitated up into view Rarity burst in causing her to jump, sending items from the drawer flying through the room.

“Sweetie Belle! It’s time to put your on your diapers for bedtime.” Rarity said already having settled into her nightwear. “Oh, I see you’ve already started.” The mare closely inspected the filly’s garment of choice before shaking her head. “Oh no, no, that won’t do at all. You’ll leak right through that, it’s paper thin!” She said, taking the pull-up from Sweetie’s hooves. “I don’t know why Mother insists on buying these cheap things, when you stay at my house you wear regular diapers.”

Sweetie Belle’s muzzle turned red, she quickly pushed the drawer closed with her magic to prevent Rarity from seeing that there were indeed multiple different choices to pick from. “Rarity! Mom said I don’t have to wear those unless it gets bad! I’ve been doing really good see!” She exclaimed, pointing to a chart above her dresser which had in the past week not had good results. “Well, last month was good!” She continued, stomping her hoof on the floor again. “Now get out of my room!”

“Absolutely not!” Rarity scolded, “Lay down please, I don’t need to embarrass you any further do I?” She asked levitating the filly to her bed before dropping her gently onto the comfortable mattress.

The small filly let out a squeak, being levitated around by Rarity wasn’t exactly her idea of fun. “Rarity!” She whined; “I can do it myself!”

“The last time I let you do this yourself, you didn’t fasten the tapes properly and wet right through to your sheets. I already told you I don’t plan on doing any laundry.” Rarity said unfolding the diaper. “Really though dear, it’s nothing to be embarrassed about.”

The small unicorn’s face scrunched in response. “I don’t need to wear that kind though!” She protested, trying to push the diaper away with her hooves. “You just want to feel like you’re better than me or something!”

“You’re being ridiculous! I’m only trying to help you prepare for bed, you wouldn’t want your friends to find out about this little problem would you?” Rarity threatened, easily bypassing the filly’s hooves and sliding the diaper beneath her plot.

Sweetie Belle’s eyes went wide, her resistance going away instantly as the older unicorn proceeded to diaper her. “You wouldn’t.” She mumbled, crossing her forehooves, knowing that further protest would only result in more problems.

“I’m not going to tell them anything, I’m your sister not a bully.” The older unicorn said with a small sigh, “If you had just cooperated from the start we could have had this done much easier.” Rarity said applying rash cream liberally to the filly. “There it’s finished, don’t stay up too late.”

The filly only replied with a sigh and a small grumble as she rolled over onto her belly before lifting herself up with her hooves. Each movement she made resulted in an embarrassing crinkling noise, her ears twitching in response to it each time. As she watched Rarity leave her room she was left with the mess of diapers and supplies to clean up from earlier.

Several hours later, Sweetie Belle stirred in her bed, ready to enact her plan. She had struggled to stay awake this late but knew it was the only way. “All I have to do is not trip over anything and get this done then I can go to sleep.” She whispered to herself, climbing down out of her bed, ignoring the crinkling from her behind.

She crept down the hallway slowly, each step bringing a familiar soft crinkle. With each crinkle she felt her cheeks growing warmer, ‘Stupid diaper, stupid bedwetting!’ the filly thought. After several minutes of slow walking Sweetie Belle arrived in the kitchen, being a little small for her age she stood on the very tips of her hind hooves, reaching up toward the cupboard where the bows and plates were kept.

Again she was reminded of the thick bulk wrapped around her behind, furthering her embarrassment. “Rarity will never expect this, I’m going to get her so good!” Sweetie mused aloud to herself, she took the bowl in her hooves and began filling it with lukewarm water. Once the bowl was filled, Sweetie held it aloft in front of her in her magic.

Once more the padded filly creeped down the hallway, doing her absolute best to be as quiet as possible, even managing to avoid crinkling for the most part. She arrived outside of Rarity’s bedroom, slowly she turned the doorknob, the door swinging open with a quiet creak.

Sweetie was greeted by the darkness of Rarity’s room illuminated only by the moonlight from the window and the faint embers of an earlier fire in the fireplace. She had forgotten Rarity slept without a nightlight and had to be incredibly careful not to trip over something. Slowly she crept into the room, her eyes taking a few moments to adjust to the darkness.

The filly lowered the bowl onto the floor next to Rarity’s bed as she slowly pulled the blankets back to find Rarity sleeping soundly. She slowly reached up onto the bed to pull the mare’s hoof down into the water when the room suddenly illuminated.

Rarity’s eyes opened and her horn lit up turning on the light switch quickly. “Sweetie Belle?” She asked as she turned to look at the scene in front of her; Her little sister creeping around her room with a bowl full of water. Her face turned to one of disappointment. “You know you would have gotten away with it;” She paused. “If your diaper hadn’t been so loud, the crinkling woke me up before you even walked in but I wanted to see what you were up to.”

Sweetie Belle squeaked in surprise, she hadn’t expected her sister to be awake. “I wasn’t doing anything! I just um… Wanted to make sure you had some water to drink incase you woke up and were thirsty!” She said in a rush, panicking that her master plan had been foiled.

The mare raised an eyebrow at Sweetie, clearly not convinced. “So you weren’t planning on trying to make me wet the bed by placing my hoof in warm water?” She asked as she tested the temperature of the water with her forehoof, finding it to be warm. “It sure seems like you were.” She paused. “However we can deal with this in the morning, I’m sure you must be tired, it's well past your bedtime.”

The filly frowned but nodded, “I’ll just go back to bed, I wasn’t trying to do anything I swear.” She said clearly lying and trying to downplay what she had just tried to accomplish.

“And I’ll come tuck you in.” Rarity said climbing out of bed, she yawned and followed after the filly, doing her best to not notice the bulk in the rear of her sister’s pyjamas. The older unicorn helped Sweetie back into bed, quickly pulling the pants away to see if the diaper was still taped up.

Sweetie’s muzzle turned red. “Rarity Stop!” She complained. “It’s still there.” She said, pausing when she noticed the mare was still checking. With a sigh, she continued; “No, it’s not wet.”

“Sorry, but I do have to check these things.” The mare said once satisfied that her sister was still dry. “Goodnight Sweetie Belle, please no more pranks tonight, okay? I’ll let this slide but if I catch you doing something like that again, I will have to tell Mother about it.” She said pulling the blankets over her younger sister. “If you keep acting like a foal though, maybe I’ll keep you in diapers tomorrow!”

The filly squeaked, frowning at the idea. “Goodnight Rarity, I won’t do anything else! I promise.” She said, blushing even more as she thought about the possibility that Rarity might carry out the joke as a punishment even if she didn’t try to do anything.

Rarity made sure to give the filly her favorite plushie, adjusting the covers once more so that they covered both her and the plushie. Once she was satisfied that the filly was secure in bed, she left the room and returned to her own bedroom quickly falling back asleep.

That night Sweetie Belle tossed and turned in bed; She was bothered by the fact that her plan had failed so horribly and that Rarity still seemed to be teasing her. Each time she’d dream it would quickly turn into a bad dream where she was looked at as if she was a foal by everypony around her. One particularly bad dream jolted her awake just as the sun started to come up.

The filly frowned as she felt the familiar cold wetness in her diaper that morning. “Stupid Rarity making me all stressed out! Making me think about being kept in diapers all day.” She grumbled to herself before thinking about the statement from last night. “Kept in diapers all day...” She mumbled as an idea formed in her head.

Slowly the unicorn climbed out of bed, not even attempting to change herself yet as she planned on laying back down. “I’ll show her!” She said walking into the hallway with her horn illuminated. She checked to make sure Rarity was still asleep before casting a spell. The doorknobs of all of the bathrooms in the house glowed the light green of Sweetie’s magic as she proceeded to lock each of them with a spell that would prevent the older mare from entering.

Her horn fizzled out and she giggled to herself. “Now we’ll see who the real foal is.” She said before returning to her bedroom, climbing back into bed to try and get a few more hours of sleep to make up for the rough night she’d been having.

A few hours later, Rarity awoke from her deep slumber feeling refreshed despite her sister’s antics. “Sweetie Belle?” She called heading toward the kitchen to prepare the two breakfast. “Did you stay dry?” She asked with a short giggle, knowing full well that her sister had likely not stayed dry at all.

The filly yawned as she slowly walked down the stairs. As she entered the kitchen she plopped herself down on one of the chairs around the kitchen table. “You already know the answer to that.” She replied, feeling the cold padding squish around her rear when she sat down. She hadn’t bothered to change yet, she was still a bit too tired to put the effort in.

“Well why don’t you get changed dear? It can’t be comfortable wearing that soaked diaper.” The mare said pouring the filly a glass of juice. “Breakfast will be a few minutes still, so you have time to clean up and prepare for the day.” Rarity said hearing the audible squish when the filly had sat down at the table.

Sweetie Belle yawned again. “I guess you wouldn’t know.” She mumbled. “In a bit, I’m still too sleepy; I’ll change after breakfast.” She said, not realizing in her tiredness that her choice of wording implied changing into another diaper.

After a small but fancy breakfast for the two ponies, Rarity decided it was time to freshen up and get ready for the day. “I’m going to have a bath, do you need the fillies room before I run the water?” She asked clearing the table of plates, and their glasses.

The filly rolled her eyes. “I’m not a foal Rarity, you don’t have to ask. Besides we have more than one bathroom.” She stated, not remembering her earlier magical shenanigans. “I’ll go change out of this stupid thing while you do that.”

Rarity sighed, “They’re not stupid Sweetie Belle, they keep your sheets dry don’t they?” She asked mostly rhetorically before heading to the bathroom. The mare walked down the short hallway to the door, she tried to turn the knob finding that it only jiggled in response. She frowned and tried once more, but the door refused to budge. “Sweetie Belle!” Rarity called out, her panic beginning to rise.

“Wait a sec!” Sweetie yelled in reply from her room upstairs. The faint sound of crinkling could be heard as she presumably was removing her diaper before several thuds that resembled the sound of the filly’s hooves carrying her to the top of the stairs. “What?” She asked, looking down the stairs seeing Rarity in the hallway at one of the bathrooms. “You don’t have to yell!” She huffed. “It makes me think I did something bad!”

“The door won’t open.” The mare deadpanned, she tried it once again but the door didn’t move.

“Did you try the upstairs bathroom?” Sweetie Belle asked, still in a sleepy morning haze as she illuminated her horn, opening the upstairs hallway bathroom door. “See, works fine!” Suddenly the gears in her brain started to turn and she remembered what she had done; She quickly closed the door again before Rarity could move. “It’s only a door.” She stated, “You don’t need help from a little filly like me to open it.” Sweetie mocked.

“What did you do to the door, Sweetie?” Rarity asked growing frustrated with every passing second, no matter how hard she tried the door wouldn’t move. “Mother said no magic!” She whined, feeling a growing need in her bladder to go.

“Maybe it’s not magic! Maybe I didn’t do anything!” The filly protested, knowing full well that she had used magic and had done something. “Only foals can’t figure out a bathroom door.”

“Sweetie, please, I can’t open any of the bathroom doors at all. I don’t know what kind of prank you’re pulling on me but it’s not funny!” Rarity huffed in frustration. “I’ll make you unlock the door if I have to.” She said angrily, horn glowing briefly. In that moment the mare had forgotten about her imminent need to use the fillies room and lost control for a few seconds. Long enough for a small dark patch to appear on the floor below.

Sweetie Belle circled around Rarity, eyeing her up and down before she noticed a small wet spot forming around her sister’s hind hooves. A dark patch formed on the mare’s fur and the puddle grew larger. “Looks like you’re having an accident.” She said with a small giggle. “Would be such a shame if anypony found out about that!” Her giggles turned into laughter. “Mom said I was in charge, and you know the rules!” Sweetie exclaimed. “Just like when we were little and you were foalsiting me and you did the same thing! If you have an accident it back to diapers!”

Rarity felt the colour creeping into her cheeks, they burned with her embarrassment. Not only had she just wet herself in front of her little sister, but it was the first time she’d had an accident since she was a little filly much younger than Sweetie. “T-That’s not funny, Sweetie! I’m not going to wear a diaper.” She said stamping her hooves just like a filly would.

“Who’s acting like a little foal now?” Sweetie teased, her laughter was starting to die down but she was still giggling. “I didn’t plan on wearing a diaper either but you saw what happened last night.” She leaned in closer to Rarity. “Besides, you wouldn’t want to explain to Mom and Dad why there’s a big pee stain on the floor now would you? What would Twilight, and the girls say if they saw you now?”

“Twilight would be sympathetic, same with Fluttershy. Applejack would never shut up about it, and Rainbow Dash…” The mare shuddered thinking of how the pegasus would tease her relentlessly. “I don’t want to think about them finding out! If I listen to you, do you promise not to tell anypony about this accident?”

“I promise!” The filly exclaimed. “After all it wouldn’t be very... Generous of me to tell everypony after you agreed to listen to me.” She said, using Rarity’s own element as a tool to embarrass her.

Rarity accepted defeat and followed Sweetie to her bedroom, she frowned at the balled up diaper laying on the floor but chose not to say anything to prevent further ‘punishment’.

“I even have a diaper ready for you!” She said picking up the soaked diaper she had worn last night. She held back laughter for a moment before tossing the diaper in a nearby pail. “You should have seen the look on your face!” She bemused going over to her dresser and removing several items from a drawer including a thick, new diaper.

“Do I really have to wear one of those ones and not a pull-up?” Rarity frowned laying down on the fillies bed to prepare for the incoming embarrassment. ‘I can’t believe I’m letting her do this! This is ridiculous!’

Sweetie glanced at the pull ups before looking back to Rarity. “I don’t think they’d fit you!” She exclaimed, levitating one of them in the air and trying to stretch the sides. “They fit me just fine but not you. The regular diapers are much bigger!” Slowly the filly levitated the diaper, rash cream, and powder over to the bed. “Don’t worry Rarity, I’ll take good care of you, I promise!” She giggled as she slid the diaper under the mare’s rear, opening the cream and preparing to apply a generous amount of it. “You know how much I hate this stuff but you made me use it last night so now you can see how it feels in your fur!”

Sweetie brought several foal wipes to Rarity’s most sensitive area, cleaning it thoroughly with the passing of each wipe. “Just hold still a sec, I’m almost done!” She teased while applying the rash cream.

The mare let out an unladylike squeak when she felt the glob of rash cream being spread generously on her diaper area, it was an odd feeling to say the least. She did her best to look away from her sister when the deed was finished. “I admit that is very uncomfortable dear,” She said blushing profusely now.

“But we’re not done yet!” The filly squeaked with excitement as she continued her revenge. She opened the powder and proceeded to apply a large amount of it both to the inside of the open diaper and Rarity's now thoroughly rash protected diaper region. With little effort she pulled the front of the diaper between Rarity’s legs and held it in place with her magic as she pulled the tabs up around her waist, taping each side in place snugly. She then ran her hooves down either side of the diaper just inside the leak guards to make sure they were properly adjusted before giving the diaper a firm pat. “There you go! See I told you these ones would fit you much better! I don’t think my pull ups would fit you at all!”

Rarity got back to her hooves and felt the plush padding wrapped around her plot; She would never admit it to anypony, not even her sister, but the diaper felt good. “I’m sure they would have if we had given them a try.” She huffed, following Sweetie Belle out of the room.

“Well I’ll make sure to remember that you wanted to wear my pull ups.” She said emphasizing the statement. “Now here are the rules.” She started, turning to face Rarity. “You’re gonna be a little filly all day and I’m the big sister for the rest of the day! If you feel like you have to go, you’re not allowed to go like a big filly, you have to go potty in your diapers like a foal!” She explained as she gestured to the garment around the mare’s plot. “Since Mom likes to buy things in bulk there are plenty of diapers and supplies for her not to notice that some more have gone missing!” She paused for a moment thinking about her statement. “D-don’t think about that too much!”

“This is ridiculous!” Rarity whined, thinking there had to be a way out of this. “I shouldn’t be forced to act like a filly.” She huffed turning her nose up to her younger sibling.

Sweetie quickly interjected. “Foal, not a filly!” She exclaimed. “Well, I guess you can be a little filly. But the rules are the rules! After all, you made them when we were little.” She stated.

The mare cringed inwardly thinking back on the times she had locked Sweetie out of all the bathrooms in their parents house. She’d done it more than once as well, most of the times were after Sweetie had been potty trained. “I’ll just go play with these toys.” Rarity grumbled, sitting herself down in front of the small pile of filly and foal toys. She picked up a rattle and shook it a few times before settling on a large pony doll.

The younger unicorn smiled as she watched Rarity struggle to play with the toys. She trotted in circles around the mare inspecting everything she was doing; She knew it would only be a matter of time before nature would take its course and she’d get her full revenge. “Aw, not having fun?” She teased as she playfully pulled back the waistband of Rarity’s diaper. She wasn’t actually checking it; She knew it wasn’t used, but she wanted to enforce the embarrassment. “Just checking.” She singsonged.

“It’s not wet or the other thing!” Rarity cried in frustrating, blushing crimson at being checked like a foal. “I’m not going to use this… Thing.” She huffed still clutching the doll in one hoof but gesturing to the diaper she had on. “I’ll hold it all day if I have to!”

“Call it what it is Rarity!” Sweetie said with a giggle. “You’re the one who called them diapers when you put one on me last night.” She turned away from her sister and started to head towards the kitchen. “I’m sure you’ll try... I wonder if Mom and Dad still have those sippy cups in the back of the cupboards...” She thought out loud. “I bet you’re thirsty.”

Rarity was admittedly a little thirsty, playing with the doll was even a little fun but she wouldn’t admit that to her little sister. She didn’t really think Sweetie would find any sippy cups, she was positive her mother had thrown them out or at least put them in storage. “I would like some orange juice.” She said even smiling a little.

The sound of cupboard doors opening and closing could be heard as the filly rummaged through the kitchen. After a few minutes Sweetie returned to Rarity levitating a sippy cup in her magic. The cup looked to be well worn, a pink and purple foalish design printed on the side and the lid itself was a bright pink. “Orange juice just like you asked!” She exclaimed cheerfully, lowering the cup onto the floor in front of her sister. She hadn’t really looked at the cup until now and she noticed her name printed in small letters on the cup, it had been hers when she was little.

Rarity gratefully accepted the cup into her hooves, knowing Sweetie would scold her if she tried to use her magic. She brought the cup to her mouth and took a long drink, nearly dropping the cup several times. After she was finished she held it out for the filly to take, before going back to playing with the doll, she had an urge to colour with crayons.

Sweetie took the cup in her magic and looked over it. “This is still mostly full!” She huffed. “Don’t you wanna grow up to be a big strong mare some day?” She asked, setting the cup back down next to Rarity. “I’ll leave it here so you can finish it.”

The morning hours passed by swiftly, Rarity started to enjoy playing with her sister’s old toys. She even let out a foalish squeal of excitement when Sweetie had brought her crayons and paper. The mare drew her sister several foalish drawings, including one of the two ponies outside of their childhood home with a heart drawn around the two.

While Rarity’s enjoyment rose, Sweetie’s displeasure grew. This was supposed to be revenge for what Rarity had done to her, not playtime for her big sister. Each time the mare finished her drink Sweetie was quick to refill it, knowing that soon things would be more like the way she had planned, they had to. “Do you want something to eat?” The filly asked as she started towards the kitchen again with the empty sippy cup. Outwardly she didn’t show her displeasure, inwardly she was jealous; Why couldn’t she have fun? Why did the revenge plan make Rarity seem happier? Why could Rarity be allowed to be so care free when she couldn’t?

Rarity followed the filly into the kitchen, the short trot made her realize that she really, really had to go. “S-Sweetie Belle? I have to use the little filly’s room.” She said, gently tugging on the tail of her sibling.

Sweetie stopped in her tracks, not even turning to face Rarity. She set the empty sippy cup down on the counter, A small smile creeping onto her muzzle. “Well Rarity, you know the rules.” She paused, turning around and giving her sister a big warm smile. It took every bit of self restraint for her not to giggle knowing what was about to happen. “You’re wearing your little filly’s room” She said in a teasing voice. “You’re not ready for the big filly’s room yet. They are your rules after all.”

The unicorn mare frowned but knew she had no grounds to argue. She shifted from hoof to hoof trying desperately to find a way to relieve the growing pressure in her bladder. Rarity knew it was useless to try and hold out longer, but her last ounce of pride was on the line. Her muscles cried for release, and finally she relented.

Rarity subconsciously spread her hind legs apart, she blushed profusely her eyes widening as the first trickle of urine entered the diaper. The trickle soon gave way to a flood, her diaper eagerly soaking up the accident. Minutes passed and she was still going. Finally the hissing came to a stop, the once pristine white diaper now puffy and tinged a faded yellow. “I…” Rarity was speechless, she couldn’t think of a single thing to say.

Sweetie Belle smiled widely while she watched her sister completely soak her diaper like a foal. She used her magic to pull back the waistband of the diaper again. “Looks like somepony wet their diaper!” She squeaked, examining the diaper. “Aw look your wetness indicators are all faded~” The filly teased as she pointed to a once yellow line that was now a smudged blue line. The diaper itself was adorned with pink and purple designs but the indicator itself was rather plain. “Maybe when you’re a bit older you won’t need to have this to tell everypony how wet you are!” She exclaimed. “But I don’t think you’re ready for a change yet, let’s go play some more!”

“If you insist, you’re the big sister after all.” Rarity said dejectedly, she sat back on the floor feeling the squish into her plot, she shuddered realizing just how utterly soaked the diaper was. Though it pained her to admit this to herself, the warm and wet padding did feel much better than she had been expecting it to.

The younger unicorn let out a small gasp. She hadn’t expected Rarity to just agree to what she had said. “O-okay!” She nervously exclaimed. “Let’s go colour some more, you had fun earlier with that. Just tell me if you have to go again so I can change you first.” She said, frowning at her next thought. “I don’t want to have to clean up pee off the floor; Again.”

Rarity huffed at the comment, “If somepony hadn’t locked all the bathroom doors, you wouldn’t have to clean pee off the floor; Would you?” She asked resuming the picture she had been colouring prior to her accident. She stuck her tongue out at her sister in a very foalish display of anger.

Sweetie huffed. “That’s not the problem here!” She stomped a forehoof on the floor. “If you hadn’t been so mean about me needing to wear diapers cause I pee- I m-mean my night time problems. We wouldn’t be talking about this right now!” She angrily explained. “I blame you! It’s your fault!” She said before sticking her tongue out right back at her older sister.

“Please, you do wet the bed, don’t be such a foal and call it ‘peeing the bed’. At least I don’t have to wear diapers to every sleepover, or have somepony chaperone while I practice Magic!” Rarity shot back, fuming at the filly’s comments. “I’ll prove that I’m the adult by not using this diaper anymore.” She said crossing her forehooves in defiance, knowing that what she said about not using the diaper wasn’t true.

The filly’s felt her cheeks heating up as they turned red in embarrassment. “It’s not my fault!” She retorted. “I don’t know why I do it! I can’t control it! If I could do you really think I would?” She yelled, her eyes watering up. “And just because I need a chaperone while I practice magic doesn’t mean anything!” She paused. “It means my magic is just more powerful than yours and I need somepony to help control it!” She said, making up an excuse. She was trying desperately not to lash out further at her sister, or cry; She wanted to do something, anything but have this argument.

Rarity sat in silence for several minutes, she realized after she’d made her comments about Sweetie’s issues that she had gone too far. She slowly got up off the floor and turned to face her sister, holding her hooves open to her. “I’m sorry. That was too far, I didn’t mean that Sweetie.” She apologized, taking a hoofstep closer to her.

Sweetie turned away, closing her eyes to stop herself from crying. She took a few breaths and composed herself. “Sometimes.” She took a long pause. “I don’t think you understand at all.” She sniffled. “You treat me like a little filly even though I’m growing up and have a cutie mark now. All I ever wanted was for you to be proud of me!” She explained, turning back to Rarity. “But all you do is tease me and embarrass me. Look at how you treated me last night! You just took a diaper instead of one of my pull ons that would have been perfectly fine, and made me wear it and called it a diaper and stuff! You knew that it bothers me! It took years before I could even sleepover with Apple Bloom or Scootaloo because of it, I still worry now even though they know!”

“Sweetie Belle,” Rarity said gently, “We both know the pull-up wouldn’t work, everytime you wear them you leak right through. I’m sorry I forced you into the diaper though, we should have tried the pull-ups first. I was too focused on making sure everything was perfect for me that I didn’t think about how you were feeling.” She sighed with regret. “I know I keep treating you like you’re just a little filly but the truth is, in my eyes you’ll always be that little filly. No matter how big you grow, or how many ponies you help with their cutiemarks you’ll always be my little sister.” She explained quietly.

The filly leaned into the older mare, finally accepting the hug. “Maybe sometimes...” She started. “Sometimes I don’t wanna be the little sister.” Her ears fell on either side of her head. “Just once I want to be a big sister! I’m always the little sister, the foal, the younger one.” She explained. “Everypony aside from Scootaloo and Applebloom treat me that way too! I just want to be able to feel like I’m a young mare like I should. But you never let it happen.”

“Well…” Rarity said trailing off, blushing at the thought that had just occurred. “I don’t always want to be the big sister. Sometimes I don’t want to have all these responsibilities of running my dress shop, or my boutique here in Ponyville. There are days when I wish I could be younger and carefree, not running around all over Equestria for fashion shows.” She frowned, shifting her hindlegs uncomfortably, the diaper had started to become cold and clammy around her waist. “S-Sweetie Belle? Could you please change my diaper, and let me be the Little Sister today?”

Sweetie’s eyes lit up as she looked at Rarity. “R-really? Even after all I did to you today? You want to wear another diaper?” She asked, letting out a small giggle. “You’d really let me be the big sister today?”

Rarity nodded, pushing Sweetie over before nuzzling the filly fiercely. “Yes, Sweetie Belle I want to wear another diaper and you to be the big sister today.”

The younger filly smiled. “Let's get you changed then!” She said, bringing herself to her hooves and leading Rarity back to her bedroom. Her horn lit up as she levitated a fresh diaper, wipes, powder and rash cream over to the bed. “Lay down for me please!” She sing-songed.

The mare climbed onto the bed and lay back, she blushed when the tapes of her diaper came undone in one swift motion. “I’m starting to understand why you find this so embarrassing,” Rarity said feeling the diaper come away from her sensitive area, she sighed in relief at the fresh air.

Sweetie Belle nodded. “Mhmm.” She hummed, not directly acknowledging the statement. “You really soaked this one! Seems like some little filly needs potty training soon!” She teased with a small giggle. She thoroughly cleaned the urine off of Rarity before sliding a fresh diaper under her. With a gentle touch of magic she applied the rash cream and a thorough dusting of foal powder before pulling the diaper up between her sisters legs. She threaded the mare’s tail through the tailhole before taping the front tabs snugly in place.

“All done little filly!” The smaller unicorn said giving the fresh diaper on her sister a soft pat. “Nice and dry so you can play!”

Rarity squeaked at the pat on her padded rear, the pat sending a small puff of foal powder out of the diaper. She scurried off down the hall back to her latest drawing, causing her sister to sigh and give chase. Once back at the drawings she laid herself down and began to draw a picture of herself and her sister together, this time with Sweetie as the big sister.

The hours passed as the two continued playing through the day. Rarity would be changed at least once more before nightfall. As the sun started to set and the two began to settle in for the night Sweetie Belle let out a yawn.

The filly had enjoyed the day after the argument had been resolved but something had started to bug her as the day went on. In the back of her head she saw how happy Rarity had become being so carefree and she realized that she also wanted to not worry about anything. As the sun fell behind the horizon and the sky grew dark she turned to her sister. “Rarity?” She asked. “D-do you think maybe...” She hesitated. “We can both be the little sister tonight?”

Rarity giggled, “What do you mean?” she asked getting the changing supplies out for both of them.

“Well, you played the little sister... But you played a really little sister.” She blushed. “I like being the big sister a lot!” She said quickly. “B-but I think I wanna be younger, like you pretended to be sometimes too.”

“Of course you can be Sweetie! In fact, why don’t you be my playmate?” Rarity asked blushing a little, “It would be fun to have somepony else to play dress up or draw pictures with.”

Sweetie only replied with a smile as she rolled onto her back to prepare for her night time diaper. She knew tomorrow would likely include many diapers for both of them and she was perfectly okay with that.

The End!