Author's Notes:

Twilight Sparkle gives Rainbow Dash a spanking, and in turn Rainbow Dash ties Twilight up for three days. During which Twilight gets gassy. And before long she has to pee due to all the drinks Rainbow gives her. Can she hold it? What led to the spanking in the first place? And did Rainbow give Twilight a disproportionate punishment, or does someone have a fetish (or a whole bunch of them)?

This chapter (and the next two) were initially posted as separate stories, but since they would be deemed too similar to each other, I played it safe and made them all chapters of the same story. Because it's basically the same thing, just with a different pony and way they got into it.

Rainbow Dash was laying over Princess Twilight Sparkle's knee. Rainbow wasn't wearing anything, while Twilight was wearing a sports outfit consisting of skintight red shorts and a dark blue tank top. They were in a room somewhere in Twilight's castle, and the other ponies were away at the moment.

Twilight brought her hoof down on Rainbow Dash's rear as hard as she could. Rainbow let out a squeal, and Twilight swatted her again, and again. Once she had spanked her 20 times, she stopped, and Rainbow Dash's butt hurt.

"How do you like that?" said Twilight.

Rainbow Dash rubbed her butt with her hoof, then turned around, a mischievous look in her eyes. "Now it's your turn!"

She moved faster than Twilight's eyes could follow. Within seconds, Twilight's front hooves were tied together in front of her, her back hooves were ties together as well, her wings were tied to her sides, and a cloth had been wrapped around her horn so she couldn't use magic.

Twilight struggled against the ropes, but they had been tied tight. She was completely helpless.

"So, what should I do first?" said Rainbow Dash. "First I'll do to you what you did to me!"

Twilight's current position made this easy, as her behind was in the air. She tried harder to get free, but it was no use. Rainbow Dash slapped Twilight's butt as hard as she could, and she could slap a lot harder than Twilight. She swatted Twilight's rear again, and again, and again. After the 20th swat, Twilight's butt was in more pain than it had ever been in her life.

"How's that, Twilight?" said Rainbow Dash.

"My butt hurts," said Twilight.

"Let me fix that for you." Rainbow started massaging Twilight's rear. It felt so soft against her hooves, and she loved the feeling.

Twilight also enjoyed it, despite her current situation. Already her butt was hurting less. She closed her eyes in relaxation as Rainbow continued rubbing her tush.

Then Twilight accidentally farted in Rainbow Dash's face. She blushed, and Rainbow Dash laughed, before getting a hold of herself and rubbing Twilight's butt again.

Once Rainbow was done, she poured some soda into a cup, as there were many cans of soda in the room, and gave one to Twilight. Twilight had to accept, for it was hot in the room and she was really thirsty. She drank 20 cans of soda without even counting, and Rainbow was snickering for some reason.

BUUUUUUUUURP!

Twilight blushed a little, and giggled nervously. This was such an unprincesslike thing to do, but the worst was yet to come. For Rainbow Dash had put fart powder in each and every cup of soda.

Within a minute after her last drink, Twilight's stomach started gurgling. Was she hungry? No... this was something else. Before long the pressure was building up inside her and she moaned.

"Twilight, you feeling all right?" said Rainbow Dash, trying hard not to laugh.

Twilight tried to break free of her ropes again. She tried using magic to untie them, but the cloth on her horn kept her magic from working.

PPPPPPPPFFFFFFRRRRRRRT!

Twilight farted loudly. She blushed, and Rainbow Dash fell on her back laughing hard.

"It's not funny Rainbow Dash!" said Twilight. She farted again, and again, each fart as long, loud, and wet as the last.

"Phew, Twilight, what did you eat?" said Rainbow Dash as she took a whiff of Twilight's farts.

Twilight didn't answer. She let out a longer, wetter fart than before. Rainbow loved it.

BBBBBBRRRRRRRRRRRRAAAAAP!

A long, deep-pitched fart made it way out of her, and soon after that, a loud, boisterous, wet fart. Twilight thought she might have made a mess in her shorts, and she couldn't even check because her hooves were tied together.

Rainbow Dash was staring directly at Twilight's butt, which had no brown spots at the moment. However, by the time Twilight's farting had subsided, and the smell had dissipated, her shorts still smelled like farts. Rainbow Dash sniffed Twilight's butt several times.

About an hour later, Twilight said "I have to pee... really bad!"

"Just hold it," said Rainbow Dash.

"How long are you planning on keeping me tied up?"

"About three days."

"Three days?! I can't hold it that long!"

"Then things are about to get really wet!"

Twilight held it in for another hour, during which she desperately tried to get free of her ropes. But Rainbow had tied them too tight for her. She was about to have an accident in her exercise shorts, and there was nothing she could do about it. She really needed to go, and Rainbow wasn't about to untie her anytime soon.

She moaned as she could feel her shorts getting damper. What started as a few spurts became a steady stream that Twilight couldn't stop. She couldn't hold it any longer. Rainbow Dash saw Twilight's shorts darken, and a puddle grow beneath her, and snickered.

Twilight blushed as she peed herself, but the release felt wonderful after desperately holding it for so long, and she sighed in relief. "Ahhhhh, that's better." After a minute she noticed she was still peeing. She had never peed for this long.

She peed for a minute and 20 seconds, and lay there in her puddle for about half an hour, still in shock at her accident. She had not wet herself like this since before magic kindergarten.

"Can you clean this up?" said Twilight afterwards.

"I don't see why not," said Rainbow Dash. She moved Twilight out of her puddle and mopped it up. Then she gave Twilight a big plate of brown beans, and many glasses of water that tasted funny. Rainbow had put fart powder in them too, and on the beans, as if they weren't enough on their own.

Twilight let out a series of loud, wet farts, some of which were as long as 15 seconds, while Rainbow laughed her butt off. Twilight stopped farting around sunset.

"Can you let me change out of these shorts?" said Twilight. Her shorts were still damp and smelled of urine and farts.

"Nope!" said Rainbow Dash. "You're sleeping in your wet shorts!"

"About that... I have to pee again. Really bad!"

"Just go," said Rainbow Dash. "You'll feel better."

"I don't want to do that again," said Twilight. "Can't you at least pull my shorts down?"

Rainbow shook her head.

Twilight fidgeted for about half an hour.

"I don't think I can hold it," she said.

"Then let me help you," said Rainbow Dash, and she moved Twilight so she was laying on her back, and began tickling her hooves with her wings.

Twilight started laughing hard, unable to even flail her legs because they were tied together.

"Rainbow! HAHAHAHAHAHAHA! Stop! HAHAHAHAHAHAHAHA! I'm gonna pee! HAHAHAHAHAHAHA!"

Rainbow only tickled harder, and within a minute, Twilight wet herself again. She didn't stop laughing until Rainbow stopped tickling about a minute later. Twilight lay in her puddle, out of breath, looked down at her wet shorts, and blushed. She had wet herself like a little filly twice in the same day.

Rainbow left her where she was and let her sleep in that position, in her puddle of shame.

...

Next morning, the puddle had dried up from the heat in the room, but Twilight's shorts were still damp. Rainbow Dash got her back into her previous position and gave her lots of drinks spiked with fart powder, and lots of beans and other stuff that would make her fart.

PPPPPPFFFFFFFT! BRRRRRRT! PPPPBBBBTTTTHH! PPPPRRRRRRT! BRAAAAAAAAP!

Twilight had never farted so much at once. Rainbow Dash laughed so hard Twilight thought she was going to pee all over the floor, but she didn't. Although Rainbow was peeing in front of Twilight whenever she needed to go, but kept herself dry.

"Rainbow... I have to go... bad!" said Twilight after a few hours.

"You know what to do!" said Rainbow Dash.

"I can't," said Twilight.

"Not even if you're thinking of rivers? Raging rivers flowing into waterfalls, splashing into a lake below?"

Twilight felt some pee leak into her already-damp shorts, causing her to whimper.

"Think of ponies splashing around in pools of water! Think of fillies jumping in puddles on a rainy day! All the rain coming down! Drip... drip... Splash!"

Twilight couldn't hold it anymore. Her bladder released itself into her shorts again, soaking them in a matter of seconds and forming a puddle under her. Rainbow Dash looked satisfied.

By now Twilight smelled really bad. In addition to the pee and farts, she was sweating a lot in the heat of this room.

Rainbow Dash slapped Twilight's butt 10 times. Twilight blushed lightly.

Before nighttime, Twilight peed two more times, and farted more times than she or Rainbow could count.

...

The next morning, when she awoke, Twilight's shorts were wet and she was in a puddle. She had peed in her sleep. She hadn't expected this to happen.

Rainbow Dash chuckled and cleaned up the puddle.

After drinking more water, juice, and soda, countless more farts, and peeing herself again, Twilight felt another sensation she hadn't felt in a few days. "Rainbow Dash! Untie me now! I have to go!"

"Just go in your shorts," said Rainbow Dash, who for some reason was wearing a similar exercise outfit, consisting of a red tank top and skintight dark blue shorts.

"I don't have to pee this time!" said Twilight.

"Oh," said Rainbow Dash. "Well, that doesn't change a thing!"

Twilight tried again to get free of her ropes, for the first time since two days ago. But the pressure in her bowels was growing heavier. After an hour of desperately holding it...

PPPPPBBBBBBLLLLLLSSSSSSSSHHHHHH!

Twilight blushed beet red as she released a wet, brown, noisy mess into her shorts. Rainbow Dash noticed the brown stain that quickly appeared on her butt and laughed so hard she wet herself. Twilight hardly noticed, due to her own, messier accident.

BBBBBBLLLLLLLRRRRRT!

Twilight could feel a wetter, messier wave of manure make its way out of her rump and into her shorts. Rainbow laughed even harder. Then Twilight messed herself a third time, and Rainbow laughed even harder, wetting her shorts again.

Rainbow left Twilight in her current state until she peed again a few hours later, and then she got her into a sitting position so that her big mess squished beneath her rear. Twilight thought the sensation was weird at first, but then, she giggled a bit...

After about ten minutes, Rainbow got Twilight back into her old position. She peed twice more that day and farted about a hundred times.

At sunset, Rainbow Dash, who hadn't changed out of her wet shorts, lay down next to Twilight. Twilight was wet, messy, and smelled really bad, but Rainbow didn't mind.

"I'll say it again, your fetishes are way more extreme than mine," said Rainbow Dash. "To think I thought my spanking fetish was weird."

"I hope you aren't too freaked out by all this," said Twilight.

"I thought it was really funny, and even if I didn't, I'd never be freaked out by any of your fetishes," said Rainbow, and she kissed her lightly. "Are you wishing you'd asked for less than three days?"

"No, this has all been perfect. Exactly like I imagined it. I hope some of my lines didn't sound too convincing."

"No, you already told me you'd say stuff like that, and to only listen if you asked me to clean up the puddle, or wanted a drink."

"Did I turn up the heat too high?"

"It's hot, but I can take it if it means making this perfect for you." Both for sweat and motivation to drink more.

"Back there... did I spank you too hard?"

"I like it harder. Next time give me all you've got!"

"I did, but I'll work at swatting harder if you want."

"Did I put enough fart powder in your drinks?"

"More than enough!" Twilight sounded really enthusiastic now. "I've never farted so many times at once! It was so... I can't describe it! I hope it didn't bother you."

"Are you kidding? Didn't you hear me laughing? It's like, the funniest thing ever!"

Rainbow Dash had said this a few times before, but it was only now, when she had said it right after hearing her fart repeatedly for three days, that Twilight was completely reassured that Rainbow Dash had found her rather unladylike interest amusing, a trait she was sure wouldn't be seen in most other mares. She had forgotten that she had even pretended to be offended at Rainbow Dash laughing at her farts.

"The smell isn't too much, is it?" said Twilight. She imagined that Rarity would faint if she smelled her now.

"I don't mind. I actually kinda like it. I'd sniff your butt right now if you want."

"That's very sweet, but right now just lay here with me."

Twilight farted again, and giggled, all pretense forgotten now that the day was almost over. Rainbow Dash had to pee, having drank several cups of water due to the heat in the room, so she just let it all out in her shorts. Twilight felt Rainbow's puddle grow under her, but she loved it.

...

The next day, Rainbow untied Twilight, who took a much-needed bubblebath with Rainbow. Both mares farted in the tub, much to their amusement.

And Twilight didn't wet the bed after that, except on nights where she deliberately drank too much water before going to bed.