It was another beautiful day in Ponyville. Sunlight could be seen streaming into the bedroom on the second floor of the Golden Oaks Library. Birdsong could be heard coming from outside as ponies went about their morning business.
A purple magical aura enveloped the drawstring of a nearby set of curtains, tugging sharply at it and drawing fabric across the window, darkening the room. A soft moan and the rustling of sheets could be heard as Twilight Sparkle tried to collect herself enough to do more than shut out the light of dawn.
Yawning and stretching, Twilight could feel some of her joints popping and shifting as she shook off the soreness of sleep. Something felt different this morning, the tired alicorn thought to herself as she shifted about on her bed. Moving her hooves to her eyes she began to rub the sand out that had collected there. As her vision cleared a disturbing scene unfolded before her. The sheets of her bed appeared discolored with moisture and her muzzle detected the acidic smell of urine. Shifting her gaze to her still sleeping partner, the wetness appeared to extend all the way underneath Rainbow Dash who remained blissfully unaware, slumbering on what was almost certainly a ruined mattress.
Clearing her throat, Twilight Sparkle addressed her marefriend. "Rainbow, wake up."
Rainbow Dash moaned and rolled over continuing to snore.
"Rainbow!" Twilight demanded.
Rainbow moaned at the increase in volume before responding. "Not so loud Twi, I have a headache. I must have drank like nine ciders last night."
"Well, that would certainly explain why you wet the bed," Twilight responded coldly.
On the mentioning of the accident Rainbow’s eyes popped open and she immediately took wing, hovering over the soaked bed with a soft cry of alarm. Fixing her gaze on Twilight, Rainbow's eyes narrowed, her brows slanting down aggressively. "What do you mean I wet the bed? The wet spot clearly extends underneath you," Rainbow pointed out.
Twilight rolled her eyes at the accusation. "I'm not the one who had nine ciders last night. Besides, I haven't wet the bed since I was fourteen."
Rainbow's eyes widened at Twilight's statement. "Yeah, well, you had at least six ciders last night-" Rainbow said before throwing up her hooves. "Besides, I haven't accidentally wet the bed since I was five." Rainbow’s tone remained confident, deciding that any intentional bed wetting probably didn't count.
Twilight Sparkle huffed. "I don't have time to argue with you about this rainbow, I'm probably going to need two showers before I open the library.”
A look of realization crossed Rainbow's face before she eyed the door to Twilight's bathroom.
Twilight continued to berate Rainbow. "And furthermore this is probably going to put my behind in- what are you looking at Rain- no, no no no you are not taking a shower before-"
But it was too late; in a flash, the athletic pony made a dash for the bathroom, holding a pillow over her tail to foil any of Twilight's attempts at restrictive telekinesis.
Twilight's horn flared with magic as she stared smugly at the pillow in her magical grasp before leaping from her bed and banging on her bathroom door. "Rainbow Danger Dash, you get out here this instant!"
The sound of a shower turning on could be heard in the other room. "Sorry Twi, I can't hear you over the sound of your shower. You're just going to have to wait for me to finish."
Twilight fumed as Dash continued her shower. Thoughts of all the terrible things she would do to the brash pegasus swirled in her head.
Eventually the shower stopped and the door to the bathroom opened. Dash made her way out, wrapped in a towel with a purple star motif. Kissing Twilight on the cheek, Dash smirked. "Shower's free. See you after work Twi." Opening a window, Dash crouched before launching herself out of the room, leaving behind a fading rainbow contrail and a dampened towel bunched up on the floor.
Twilight sighed dejectedly as she picked up the towel and made her way into the bathroom to clean herself and make ready for the day.
Twilight's ear twitched in annoyance as she went through her daily reorganization of the library's various books. Everything felt off about today. Twilight felt like she was having a hard time organizing the books correctly. It felt like it had taken forever to get clean this morning and her fur still itched where she had been laying in Rainbow's accident. "Why can't she just be a grown mare and admit it?" Twilight said quietly to herself.
"Admit what?" a curious Spike asked, shelving books alongside Twilight.
Twilight looked down, having forgotten that Spike was right there assisting her. Blushing slightly, she replied, "Nothing, Spike, don't worry about it."
Spike looked at Twilight quizzically. "Are you sure everything’s alright, Twilight? You've been grumpy all morning."
"I have not been grumpy all morning," Twilight said with a roll of her eyes. Turning around, she made her way toward another stack of books to be shelved, tripping over a low hoof-stool in the process. With a loud yelp, she crashed to the ground, streaks of light dominating Twilight’s vision.
"Twilight! Are you alright? I didn't mean to put that stool there, it was an accident!"
Twilight shook her head clearing the stars from her eyes. Lifting a hoof to her temple, she rubbed it softly. "That's alright, Spike, accidents happen."
"I should still be more careful. You can prevent accidents from happening if you just prepare for them," Spike said, moving the stool to a more appropriate spot.
"Prepare for an accident?" Twilight said aloud. "How do you prepare for something you don't know is going to happen?" Twilight continued to ponder the question, her thoughts drifting to the events of that morning. "Wait a second; if I make an accident happen but prepare for it, I can prove I was right!" Twilight shouted excitedly.
"Make an accident happen? Twilight you're not making any sense," Spike said, putting some books away.
"Spike I need you to do me a favor. Run down to Sweet Apple Acres and get fifteen bottles of cider from Applejack. I've got some shopping to do.”
That evening, Rainbow Dash made her way back to the Golden Oaks Library. She was exhausted from working all day and getting in a little stunt flying practice. Opening the front door to the library, she was surprised to see Twilight greet her with a smile on her face. "Hey Twi, how's it going?" Rainbow asked casually.
"Oh, I'm doing great, Rainbow." From behind her back Twilight produced an ice-cold bottle of Applejack's famous hard cider. "Thirsty?"
Rainbow Dash's tongue fell out of her mouth as she saw her favorite treat being offered to her. Reaching out a hoof she suddenly stopped short. "Wait a second, I was kind of a jerk to you this morning. Why are you being nice to me?"
"Because I know I was right about this morning and I have a way to prove it," Twilight said, smirking.
"What? You have no way to prove that was my fault," Rainbow said, taking the cider from Twilight and twisting the cap off with a satisfying hiss.
"Oh, I think I do. If you're pony enough, follow me upstairs." Twilight swished her tail back and forth alluringly as she ascended the stairs to her room.
Rainbow smiled wryly and took a satisfying swig of her cider before following her marefriend upstairs. On reaching Twilight's room, Rainbow Dash gasped, spotting a wooden tub filled to overflowing with crushed ice and bottles of cider. The wooden tub was sitting next to something covered in a purple sheet. Twilight walked over to the tub, grabbing a drink for herself.
Rainbow smiled and drained the rest of her cider before putting the empty bottle on the floor. "I'm all for drinking more cider but what is waking up in another wet bed going to prove, Twi?"
Twilight continued to smirk. "Oh we're not going to wake up in a wet bed. We'll be wearing these," Twilight said, as her magical aura pulled away the purple sheet revealing a bag of Silly Fillies diapers.
"Diapers?" Dash asked incredulously. "You’re joking, right? Those are way uncool."
"If it turns out that I was the pony that wet the bed, I'll do whatever you ask for an entire day."
"Deal," Rainbow responded immediately. Picking up another cider, she popped the top before toasting with Twilight.
"You're the besht mare friend ever, Twi," Rainbow said, sloppily nuzzling Twilight. Afterwards, Rainbow set the last of the bottles of cider on the floor.
Twilight hugged Rainbow in response and yawned deeply. "I think it'sh time for bed, Rainbow."
"OK," Rainbow said, yawning deeply herself. Rainbow glanced over at the package of diapers. “Which of ush is going to be firsht?”
Twilight looked up. "It wash my idea, I'll do you firsht." Making her way unsteadily over to the package of diapers, Twilight opened the bag and pulled out two of the puffy garments. Gesturing for Rainbow to lay down, Twilight unfolded the wings before roughly lifting Rainbow's hooves and sliding one of the diapers under her. Lifting the front panel into position Twilight attempted to tape it shut, but her coordination was shot. Try as she might, Twilight couldn't get the garment taped up properly. "Rainbow, I can't get it to fit."
Rainbow frowned at the situation. "Twilight, what if I wet the bed? You gotta get it on right!" she said. Rainbow was seriously considering the possibility of it happening at this point.
Twilight was at a loss. If she couldn't do it then Rainbow was certainly in no position to. "Shpike? Can you come in here? I need your help with shomething."
The sleepy-eyed dragon appeared in Twilight's doorway shortly thereafter. Seeing the various empty cider bottles, Spike left and immediately returned with an empty bucket.
"No, not that," Twilight said. "I need your help with Rainbow."
Spike approached the bed and seeing Rainbow in the position she was in caused him to raise an eyebrow. "Why is she- actually, don't answer that, I'm not sure I even want to know." Spike finished diapering Rainbow and watched as Twilight laid down on the floor.
"Can you do me next?" Twilight asked, blushing furiously.
Spike sighed aloud. "The things I put up with." Grabbing the other diaper off the bed he jumped down and repeated the process on Twilight. "I'm not changing you two tomorrow morning. Good night." Spike left the room to go back to sleep.
Twilight got up off the floor with a distinct crinkling noise and crawled into bed next to a grinning Rainbow Dash. Twilight looked over at her. "What are you grinning about?"
"I'm smiling because you're a silly egghead." Rainbow dash leaned in with a crinkle of her own and kissed Twilight on the muzzle. "But you're my silly egghead.”
Twilight smiled at Rainbow's sentiment for a moment, losing herself in those half lidded magenta eyes. Caught up in emotion, she embraced Rainbow pulling her into a passionate kiss.
Rainbow moaned into Twilight's anxious mouth as she moved a hoof down her body to press the material of her diaper into her marehood. Continuing to make out, she pushed the crinkly padding against Twilight's genitals over and over again.
In her drunken state, Twilight was quickly overcome. She could feel herself being rocked by wave after wave of pleasure as her diaper became warm and sticky. Breaking away from Rainbow's muzzle, a strand of saliva lingered between them. Twilight ran a hoof over her mouth. "I love you, Rainbow."
"I love you too, Twilight," Rainbow said as she settled into her pillow and drifted off to sleep.
Twilight turned on her side with a crinkle and made herself comfortable before drifting off also.
Twilight's mouth felt dry as she awoke. Licking her lips, she decided that two nights of drinking in a row was probably her limit. Somewhat disorientated, she sat up in bed and heard a strange crinkling sound. Looking down, Twilight saw a strange white garment that felt like plastic. Suddenly, memories of last night flooded back to her and Twilight pinned her ears down in embarrassment. Still, it had been for science, and she had data to collect.
Looking over at Rainbow Dash's sleeping form, Twilight was initially disappointed to see she was still covered. Rainbow had a habit of hogging the blankets. Taking the blanket in her magic, she gently removed it from Rainbow's form, confirming her suspicion. Rainbow's diaper was swollen and slightly yellowed from use.
"Yes!" Twilight shouted a little too loudly. "I knew I was right."
Rainbow moaned and shifted, her diaper making a crinkling sound as she sat up in bed. "Well somepony certainly seems excited this morning." Rainbow rubbed her head as she opened one of her eyes.
"You didn't believe me but look, you're soaked. You clearly wet the bed the other night!" Twilight said triumphantly.
Rainbow looked down, testing her padding with a hoof before smiling. "So it would seem." Rainbow crawled over to Twilight and gave her a peck on the cheek. "But it looks like I'm not the only one." Rainbow smirked and pushed her hoof into the same spot on Twilight's diaper as before eliciting a wet squish.
Twilight felt the cold moisture against her fur and shivered before giggling. "Both of us, huh. I didn’t think of that. Sorry, Dash."
"It's alright Twilight, I forgive you." Rainbow Dash moved in to hug Twilight and they embraced for a bit.
Suddenly, while they were hugging a distinct hissing sound could be heard. As Rainbow Dash pulled away from Twilight, she could see the wet patch on her marefriend's diaper grow larger and larger. "Twi?"
Twilight looked down in embarrassment as she finished relieving herself into her diaper. "I still had to go," she said, looking up to see Rainbow's wings stiffen with an audible pomf.
Rainbow was blushing furiously before she managed to regain her composure. "Hey Twi, remember our agreement from last night? You said that if it turned out that you had wet the bed you had to do anything I say today." Rainbow said confidently.
"Oh. I did say that, didn’t I?" Twilight replied, grinning.
