Rainbow Dash's "New Costume"

by Zubric

Rating: teen
Tags: Rarity, Main 6, My Little Pony: Friendship is Magic, Rainbow Dash
Length: 2886

Rainbow Dash forgot to get a Nightmare Night costume. It's a good thing Rarity just so happens to have she needs.

Rainbow Dash forgot to get a Nightmare Night costume. It's a good thing Rarity just so happens to have she needs. Well, what's left that is.

Teen cause padding and stuff.

Co-writer: Foal Star
Cover by skitterpone

Published 2021-10-28 16:40:01 UTC
Last updated 2021-10-28 16:40:01 UTC

Rainbow's New Costume

Rainbow Dash was freaking out as she realized her Shadowbolt nightmare night costume was ruined! The daredevil mare was just staring at the dark black flight suit in horror realizing that there was a giant tear in it.

“Ugh! You have got to be kidding me! When did this happen!?” the blue-coated pegasus roared. She stomped off as she threw the costume aside.

Now the pegasus didn’t have a costume for the big Nightmare Night party Pinkie Pie was hosting. She could only hope that somepony had a spare…

“Rarity! She has to have something I can wear!” the daredevil exclaimed suddenly. She rushed off into the night. As she flew Rainbow Dash admired seeing the town decorated for the occasion, with decorations of skeletons, or ghosts hung up everywhere. The whole town was bathed in the soft orange of the setting sun looking rather eerie. Rainbow Dash had a grin on her face as she was thinking of what pranks she might pull once she had her costume. “I wonder if Luna will be visiting this year?” she thought, as Rarity’s boutique came into view.

Pulling the door open once she landed she poked her head in wondering why most of the lights were turned off with only a few casting shadows all dramatic-like. “Rarity, you in here? I have a bit of a problem.”

She then turned around to see Rarity was already dressed in a vampire costume with little bat wings sprouting from the sides, and fake vampire teeth in her mouth. The fashionista was rather surprised to see Rainbow Dash and waved a hoof. “Hello Rainbow Dash, I didn’t expect to see you here?”

“Wait, are you closing up!” Rainbow exclaimed, getting rather frantic.

The white-coated unicorn paused as she replied, “yes darling, I am? I’m assuming you’re here for a costume? How could you not have one ahead of time?” she waves her hoof in a scolding manner.”

“Yeah! I need one for the party, somehow my Shadowbolt costume had a tear in it!” Rainbow exclaimed looking even more frantic.

Rarity shook her head, “I told you darling to give it to me to fix it up for you before.”

“Yeah! I know okay!” Rainbow Dash snapped, getting rather frustrated. “Seriously, I just need a costume. I’ll even take just a bunch of bandages like a mom- I mean mummy.”

“Daww, did you just call me mommy?” Rarity teased with a snicker behind a hoof.

Rainbow rolled her eyes, “you know I said mummy, now you gonna give me a costume or what?”

Rarity trotted over to the front of her store and began to unlock it. “Well darling, you do know that my costumes are quite popular. I’m not sure what’s left.” A light smirk on the fashion pony’s face for just a moment.

“I’ll take anything! I can’t show up to a party without one.” Rainbow shouted back.

As the two walked further inside, Rainbow got rather nervous as all the racks usually full of costumes were empty. There was clearly nothing left.

“I could just cut some holes in a bedsheet and make a lame ghost costume,” Rainbow mumbled to herself.

“Oh pish posh, you will do no such thing,” Rarity replied as she took out a bunch of strange bright yellow garments. Rainbow eyed the outfit looking confused, “um...what is that?”

“It’s your costume darling! “ she unrolled it to show off its true form watching as Rainbow’s eyes went wide. It was unmistakably a yellow onesie with matching booties and bonnet along with a thick-looking white square diaper.

“No way! Is that a diaper!” Rainbow shouted flying back a little. “I am not wearing a diaper!”

Rarity narrowed her eyes at the pegasus, “Rainbow Dash, you said you needed a costume and this is my last one. You have two choices, one you wear this to the party or go with no costume at all. It’s your choice.”

The pegasus whined stomping about. She really didn’t like either decision but there wasn’t much of an option. “F...fine… I’ll wear the stupid diaper.” She was startled when Rarity magic tugged her on her back taking charge of the moment.

“Good, let’s hurry this up, we don’t want to be late.” Rarity cooed starting with the booties as she rose the pegasus’s rump in the air.

The pegasus bit her lip as Rarity went about dressing the poor daredevil into the little yellow booties first. The fashionista was gentle ensuring each one came over snuggly on Rainbow’s hooves. Then came the diaper...Rarity took out the white padded square and gently unfolded it and laid Rainbow Dash’s rump over the padded seat. As Rainbow weight sank into it, the padding made the audible crinkling sound. “Now don’t be too fussy or you’ll just make this take longer.”

Rainbow laid her head back grumbling to herself but then she felt the diaper slowly come over her rump. The mare’s cheeks flushed pink feeling the fabric hug her bottom rather tightly. She didn’t want to admit it but the diaper felt nice...like a small cloud was gently taped around her rump. Next, she was pulled up into a sitting position with Rarity smiling at her.

Rainbow’s whole face was now a beat red as she was now just sitting there with a diaper firmly taped around her waist.

“Now can you raise your hooves for me?” Rarity cooed softly as she lifted the onesie up. Rainbow Dash shook her head. The fashionista just smirked as she took a feather from Rainbow’s wing making her squeak as Rarity tickled the mare’s belly. “Achoohie coo! Come on!”

Rainbow Dash started to giggled and kick about as she was tickled relentlessly. It was rather adorable with her diaper crinkling rather audibly and with Rainbow’s hooves covered in her soft booties. Rarity took the opportunity to slip the onesie over the pegasus’s body and buttoned the bottom hatch. Lastly came the bonnet which was a simple tie around Rainbow’s muzzle.“There, we go! Now you're all dressed up and ready for the party!”

She looked back and saw that the diaper at least was mostly covered up with only some of the fabric poking from the leg holes. Although the diaper bulge left little to the imagination. She decided to walk around and squeaked, noticing an obvious waddle to her step. Rarity just stood there smiling like a mother watching her foal walk for the first time.

“So what, you’re gonna be my foalsitter?” Rainbow asked in a disgruntled tone.

Rarity laughed and shook her head. “No, of course not darling, it’s just a costume.”

Rainbow Dash squished the padding between her thighs a little, the diaper was rather thick and she was starting to feel comfortable. But there was a burning question on her mind. Rainbow looked up then asked, “so, why did you make this cos-mmmph!”

As Rainbow tried to ask her question a bright yellow pacifier was popped into her mouth by the unicorn who cooed, “enough talking dear we’re already late.”

She groaned quite angrily and continued to suckle on the pacifier, although Rainbow wasn’t sure why as she followed her out and along the street.

Rainbow blushed along the way, the colts and fillies still out collecting candy only giving a few glances, although a few did snicker.

Rainbow pouted and wanted to yell at the little foals but she just found herself suckling her pacifier which soothed her. She didn’t know why but the rubber bulb in her mouth just helped her feel comfortable. The waddle in her step was hardly noticed after a while as the music from Sugarcube Corner echoed nearby as they approached.

As they entered, Pinkie hopped over dressed up in a fluffy bunny costume as she greeted them “hey Rarity, Rainbow glad you made it,” she said with a giggle as she saw Rainbow’s attire.

Rainbow squished the padding between her legs seeing another friend now gawking at her “new costume” “h...hey Pinkie.” Rainbow lisped, “it’s just a costume okay.” Her cheeks still flushed crimson.

“Oh I know, but if you need a change let me know!” Pinkie squealed as she bounced off.

“Ugh! I’m not going to use my diaper!” Rainbow whined, stomping her bootied hoof. She gave her pacifier a few suckles and she waddled her way in further seeing all the various ponies and naturally her friends too. At least there were plenty of snacks. Swaying a bit to the music, she waddles her way closer to the gang seeing her friends' costumes.

“Howdy little one,” Applejack greeted with a snicker. She coated herself in silver paint with metal plates on her chest.

“My name is Rainbow Dash!” the mare snapped back.

Applejack snickered, “that lisp is so cute!” She had Rainbow come over to a tub full of apples in water. “Why don’t ya try and bob for an apple sweetie,” she babied which just made Rainbow blush harder.

Rainbow frowned as she looked into the tub. She was going to try grabbing one of the apples but Applejack came over and took the pacifier from her mouth. “Can’t bob apples with your paci cutie.”

“Ugh, stop it,” Rainbow whined, giving her friend a light push. “I’m not a foal,” she looked down at the reflection before dropping her head into the water, getting her bonnet a bit wet as she did.

She placed an apple down before going back down and grabbing another, then another. Rainbow was smiling seeing she was doing really well bobbing apples.

“Aww such a good bobber,” Twilight teased as she poked at the diaper bottom. Twilight wore a lab coat with black latex gloves on her legs and goggles looking like some mad scientist.

Rainbow whined as she cried out, “I don’t need a diaper check!”

“Awwww,” all of Rainbow’s friends chimed at once as the group gave her a group hug.

Pinkie giggled. “Little filly has lots of friends to make sure she doesn't get in trouble.”

Rarity smiled with a wink. “Well, if she's going to act like a foal may be one of us should take her out for candy.”

Rainbow shifted. “W-what no I mean uh maybe,” she rather sheepish as Pinkie even offered her a sippy cup of Nightmare Night punch. “Pinkie, I want a regular glass!”

“No, no, little one might spill,” Pinkie teased, letting her friend take the cup.

Rainbow had an adorable pout as she puffed out her cheeks as she sip the fruity punch.

Rarity gently booped Rainbow on the nose after a minute. “Well darling, if you didn’t want to be treated like a foal you should have been more prepared.”

“Not my fault, somepony ripped my other costume,” Rainbow grumbled as she continued to suckle down the punch.

Applejack rolled her eyes, “don’t go blamin’ ponies for your accident sugarcube.”

Twilight blushed as she added, “Talking about accidents...maybe it’s not a good idea to give Rainbow too many liquids before she goes out.”

Rainbow stopped suckling and put the sippy cup aside for a second. “I can just go potty b…” she squeaked, hearing herself just say potty like a toddler. She covered her mouth as another small round of snickering occurred. “S-shut up, it was just a slip-up.”

Mrs. Cake came on by dressed in a pumpkin costume, “oh sounds you're all having fun and did I hear somepony needs to use the potty?”

Rainbow cautiously raised a hoof. “C...can I use your bathroom please?”

“Of course, but do you need somepony to help you?” Mrs. Cake asked, poking a hoof at her diaper.

Rainbow shook her head before running upstairs. She didn’t know why but she was actually a bit nervous she would have an accident in her diaper. She was a big filly! And she’ll prove it!

After “going potty” Rainbow Dash came downstairs with her onesie unbuttoned with her diaper now fully exposed. “Ugh! Can somepony help me with this!”

Applejack came by with a smile, “Here let me help ya sugar cube,” Reaching for the buttons she easily secured the button on the hatch back in place. Rainbow squeaked a little, feeling the diaper now securely around her rump.

“Ya sure ya don’t need foal powder? Ya might get a rash.” Applejack asked.

“For the thousandth time, I'm not using my diaper! I can go potty!” Rainbow shouted not even relaxing; she was sounding more like a toddler.

“Ok, ok! Just making sure,” Applejack replied with a snicker she then gave Rainbow a large plastic pumpkin bucket. “Look, even got ya something to hold your candy.”

PInkie came up next popping Rainbow pacifier back in too, “Don’t forget your binky hehe.”

Rainbow only got a little pouty, as she did rather miss the pacifier she just let it bob up and down in her mouth.

“Well just in case you should bring this,” Twilight suggested as she then hoofed Applejack a giant dark blue diaper bag. Rainbow whined seeing it had a Shadowbolt insignia and it was much larger than any other diaper bag being obviously for her!

“Calm down, it’s for emergencies only ya just went soya should be fine until we get back.” Applejack explained as she patted the seat before taking hold of Rainbow hoof like a child. “Come on, maybe we’ll run into my sister along the way.”

Rainbow groaned hoping that they didn't know that if they met Apple Bloom, Scootaloo wouldn’t be far behind! There’s no way she can see her wearing a diaper! “This is so embarrassing,” she whined even as they went along to a few houses. The ponies seemed confused at first but soon gave the pegasus some candies as they daw or cooed at her. Not like she is the only adult that does candy collecting. The pegasus meanwhile is still red as an apple, but her pacifier helped her remain mostly calm as they went door to door.

Unfortunately, the trip through the main market undoubtedly resulted in the crusaders spotting them. Rainbow panicking as Apple Bloom called out. “Oh hey sis,” the filly chimed as the trio approached. The farm filly dressed up as a superhero, while Sweetie was a witch. Lastly, Scootaloo wore a mockup of a Wonderbolt’s flight suit.

Rainbow Dash scurried behind Applejack trying not to be seen but Scootaloo caught her and her eyes went wide. “Rainbow Dash! Is that you!?”

Rainbow whined, hiding her face behind her hooves. “It was all I could find okay! I’m still cool!” The lips just made it sound kind of cute.

Scootaloo trotted over with a smile, “aww, don’t be shy that costume is so cute! In fact, it’s actually really brave of you to wear such an adorable outfit!”

Apple Bloom chuckled. “You callin something cute, that’s new.”

“Hey if Rainbow Dash wants to be cute, then she can be cute, okay.” Scootaloo snapped back, flaring out her small wings.

Rainbow got up smiling. Scootaloo was such an amazing little filly. She trotted over and ruffled her mane. “Heh, thanks just um...don’t go telling everypony what you saw tonight ok?”

“No problem! Um, you want some candy!?” Scootaloo asked, showing her plastic pumpkin filled with all kinds of candy. “We could do some trading.”

Rainbow looked at her own bucket and sat down with a crinkle. “Okay, let’s see what you got.”

The trading negotiations over candy went on for a bit soon getting heated when it came to chocolate coins and of course neither of them wanted gum. The two were both happily laughing by the end as the group soon got up and headed along towards the forest for the candy offering part of Nightmare Night. After that, the two-headed along back to the bakery.

As they walked, Applejack nudged Rainbow on the side with a snicker. “We got you good didn’t we?”

“Huh, what do you mean?” Rainbow asked, confused.

“Well, we know you’d go for the Shadowbolt costume again so the girls and I decided to do a little prank on ya.” Applejack winked “bet there was an enchantment on the pacifier too. Hehe unless ya actually like sucking it.”

Rainbow spat the pacifier out and snapped, “seriously!? This was all a prank!”

She walked back inside Sugarcube corner with all her friends giggling.

“Alright! Who’s idea was it! Pinkie Pie!? Or Rarity! She was the one who got me all dressed up!” Rainbow roared.

“Well, it was simply payback for putting all my dress ponyquins into diapers.” Rarity said simply. “Besides, it was a harmless prank.

Rainbow waddled over seething but then gasped hearing a squishing noise. “N...n...no way!”

Twilight blushed, “oh dear, maybe my spell was a bit too powerful.”

Rainbow eyes twitched before she screamed and glared at the princess. “You are so getting it.”

“Not before we change you, sweetie,” Fluttershy cooed, trotting over in a cute fluffy sheep costume. She got out a fluffy pink changing pad and a few diaper supplies.

“Nope! No way! Not happening, I'm going home, ugh!” With that, Rainbow zipped out of the door flying toward her home as fast as possible so she could get everything off.

Fluttershy blushed, rubbing her leg sheepishly. “Um...too much?” Everypony else just burst into laughter once more.