Rainbow Dash was at a joke shop in Manehattan looking for new prank materials, and was just walking toward a container of fart powder when something caught her eye. It was a hypnosis kit. She grinned mischievously. She was going to have a lot of fun with this.

...

Rarity had just finished work on a new dress when she heard a knock at the door. She opened it, and on the other side stood Rainbow Dash.

"Hi Rarity!" said Rainbow Dash. "Wanna see a trick?"

"I don't see why not," said Rarity.

"Are you in the middle of something?"

"I just finished making a new dress. I can relax for the rest of the day."

"Good." Rainbow Dash held up her hoof, which had a sort of bracelet on it. The bracelet had a stone with a spiral design. Rainbow Dash held her hoof in front of Rarity so that the stone was next to her face. "Stare at this without moving your head."

She moved her hoof slowly back and forth while Rarity did as she was told, her eyes following it. Before long, Rarity's eyes started to get tired, and soon she was asleep standing up.

"Now, when I clap my hooves three times, you'll do everything I say!"

Rainbow clapped her hooves together three times. At the sound of the third clap, Rarity jolted awake. From her eyes, Rainbow could tell she was in a trance, and that the hypnosis kit really worked.

Now, it was time to put her plan into action. Rainbow Dash had always found Rarity very attractive, but knew that she would never satisfy her fetishes for her. They were too unladylike for such a feminine mare as her. But with this, Rainbow could make her darkest fantasies a reality!

"First, put on a sports outfit," said Rainbow Dash.

Rarity got out a light purple tank top, about the same shade of purple as Twilight, and a skintight pink pair of shorts, and put them on.

"Now, stay there and pretend you're sleeping until I return."

Rarity lay down, closed her eyes, and made sleep-like breathing sounds (not quite snoring) while Rainbow Dash flew away.

About a minute later Rainbow returned, carrying a saddlebag while wearing skintight dark blue shorts with white lines at the sides, and an equally tight T-shirt that was a medium shade of blue. "I'm back!"

Rarity stood up, still in a trance.

"Drink these!" Rainbow took five bottles of soda, each of which was two liters, out of her bag.

Rarity guzzled them down one by one. Rainbow Dash chuckled. She had emptied a full container of fart powder into each one.

"Now, when you feel the urge to fart, fart in my face!" Rainbow's heart was racing that Rarity was going to do this any minute now. "And giggle in a really girly way each time. Until then... stick your rear end in the air!"

Rarity got into a position with her head on the ground and her behind in the air. Rainbow slapped Rarity's butt. And again, and again. Despite her trance, Rarity squealed each time, which Rainbow Dash really liked.

Rainbow stopped spanking Rarity after the tenth swat. She didn't want her butt to be in too much pain when she released her from her hypnosis.

"Now spank me as hard as you can until I tell you to stop, or until it's time to fart!"

Rainbow turned around and stuck her butt in the air towards Rarity. Rarity walked over to Rainbow's tush and slapped it as hard as she could. Rainbow let out a squeal of surprise the first time; Rarity could slap harder than she thought.

About twenty swats in, Rainbow Dash's butt hurt, but she didn't tell Rarity to stop. She was enjoying this too much.

After Rarity had swatted Rainbow's rear over fifty times, she stopped. At first Rainbow was disappointed, but disappointment turned to excitement when she remembered what this had to mean.

Rainbow Dash turned toward Rarity, who turned around so that her butt was in Rainbow Dash's face.

PPPPPPPPPPPFFFFFFFRRRRRRRRRT!

Rainbow Dash laughed, while simultaneously feeling aroused. She had always wanted Rarity to fart in her face, and now her fantasy had finally come true!

BBBBBBRRRRRRAAAAAAAP!

The air in Rainbow Dash's face was thick with the smell of Rarity's farts, but Rainbow didn't mind. She inhaled deeply.

Rarity released five short but loud and wet farts, each within a second of each other, giggling just as Rainbow had said. Rainbow began rubbing Rarity's tush with her hooves, during which Rarity farted twice more, each fart lasting over five seconds.

"Now," said Rainbow Dash, a new thought occurring to her while remembering what else was to come eventually. "Sit on my head and keep farting. Get up only if I tap you three times with my hoof, or if you have to pee. And when you have to pee, let me know, and hold it until I say so. You can do the pee pee dance when it gets really bad."

Rainbow Dash lay on her back and allowed Rarity to sit on her face. Rarity's butt felt even softer against her face than her hooves, and she loved it. Her shorts smelled like farts - and Rainbow loved that, too!

FFFFFFFFFFRRRRRRRRRRT!

Rarity let out a loud fart, and giggled. Rainbow Dash was sure this would make anyone else faint, but her fart fetish and attraction to Rarity made it impossible for her to feel even the slightest bit nauseous.

As Rarity continued to fart on Rainbow Dash, Rainbow let out a loud fart of her own.

After about half an hour, Rarity stopped farting. Only ten minutes later did Rarity stand up. Rainbow Dash had not tapped her once with her hoof.

"Hey, why did you-" she stopped, for she knew there could only be one reason why Rarity had stood up.

"I have to go pee," said Rarity.

Rainbow waited, her heart beating faster, until Rarity started frantically dancing around, a pained expression on her face. She really did have to go, for much of the soda she drank had gone through her. Rainbow Dash watched for ten minutes, loving every second of Rarity's desperation.

"Now, pee in your shorts," said Rainbow. "And make whatever sounds you feel like."

Rainbow could hear a soft hissing sound emanating from Rarity as her pink shorts darkened, and pee began pouring down her legs, forming a puddle on the floor. Rarity sighed of relief; while her trance kept her from feeling shame, she remained conscious of how wonderful the release felt.

Rainbow Dash had never felt more aroused in her life. Rarity was wetting her shorts in front of her! Rainbow was so excited she peed a little. She didn't mind. It was her fetish, after all.

Once Rarity finished peeing herself, Rainbow Dash said "Now, you should have to pee pretty badly again soon. That was a lot of soda you drank. When you have to pee REALLY badly, let me know. Until then, sit down where you are."

Rarity sat down in her own puddle of pee and stared at Rainbow Dash with a cute face. Rainbow sat down too and waited patiently. Her butt still hurt, but she didn't mind. About half an hour later, she felt an urge to pee as well, and just let it all out in her shorts. She really loved the feeling, and she was going to get a lot wetter before this was over.

Just under an hour after her accident, Rarity said "I have to pee really badly again!"

"Give me a golden shower," said Rainbow Dash. She laid on her back to get into position.

Rarity stood above Rainbow Dash and peed through her already-wet shorts. Rainbow Dash loved the feeling of Rarity's pee raining down on her, soaking her mane, her T-shirt, her shorts... Within ten seconds every part of her was soaking wet.

Rainbow Dash was panting heavily. Rarity had just satisfied all her fetishes.

"Massage my butt for about five minutes," said Rainbow Dash once she had recovered from the thrill of receiving a golden shower from Rarity. She laid on her chest this time.

Rarity rubbed Rainbow's butt with her hooves. About two minutes in Rainbow accidentally farted in Rarity's face, and giggled nervously, but Rarity did not react.

After five minutes, Rainbow decided she'd had enough fun. She told Rarity to stand to the side, and cleaned up the puddles on the floor herself. Once she was sure the floor was sparkly clean, she made Rarity walk with her to the nearest big mud puddle, and told her to play around in it. Rarity did as she was told, and Rainbow played around in the mud with her.

Once both mares were completely covered in mud, Rainbow walked out of the mud. She remembered what the instruction manual had said about how to snap a pony out of their trance.

Rainbow clapped her hooves together three times.

Rarity looked as though she had just woken up from a deep sleep. Or, rather that she had just been rudely awakened from a very lovely dream.

"Sweet Celestia! What am I doing in the mud?" said Rarity, standing up immediately.

"You were sleepwalking," said Rainbow Dash. "You played in the mud in your sleep, and I played along with you cause it's really fun! I guess the mud woke you up from the sleep I put you in."

"Well I don't think it's very fun. Next time, can you wake me up before I get all dirty?"

"Sure thing." Next time she'd have Rarity make another sports outfit saying it was for her, and have her use it, then change out of it and let Rainbow take it to her laundry, then have them take a bubblebath together to clean up before she snapped her out of her trance.

...

As Rarity set up a bubble bath, she removed her shorts, and sniffed them a bit. She could have sworn she could smell urine and farts on them. She blushed profusely. Had she farted and peed in her sleep, in front of Rainbow Dash? Or... did Rainbow Dash hypnotize her into it? Did she do it because it amused her for such a ladylike mare to do things like that, or did she have a few fetishes?

She should have been disgusted that Rainbow would ever do that to her, but she only giggled a bit. She'd never consciously wet herself or fart in front of another pony, but a part of her liked that she had the chance to be really dirty, and she was sure her fantasies about Rainbow Dash were far worse.

She'd hide her suspicions and pretend not to know anything. Maybe someday she'd find a way to hypnotize Rainbow Dash back. She drooled at the thought of what she would do.

Rarity put her shorts back on, let out a quiet, airy fart, and hopped in the bathtub. She considered farting in the tub, but decided not to. She'd reserve her unladylike farting for the next time Rainbow hypnotized her, for she knew Rainbow would do it again.

Author's Notes:

Again, don't take too seriously and I know Rainbow would never do something like that in the show (Maybe Starlight would though). Much less would Rarity take it the way she did.