"Hey Starlight," said Rainbow Dash. "Can you do your magic thing again?" She held up a container of fart powder.
"Again?" said Starlight. "This is the third time this week. Don't you ever get tired of farting?"
"Nope!"
Rainbow Dash loved to consume large amounts of fart powder, because she thought it was fun to fart, and thought it was funny. Sometimes she and Pinkie Pie would have farting contests. She thought it would be fun to fart more, so she asked Twilight to magically enhance the fart powder to make it twice as powerful. Twilight vehemently refused - not only was she usually too serious to use her magic for her friends' entertainment, but she found this to be disgusting, and while she didn't judge Rainbow for her interest, she didn't want to be a part of it.
But, Starlight was a little more willing to cooperate. She didn't find it very funny, but would always cast her spell on the fart powder every time Rainbow came to her with it.
Once Starlight did so again, Rainbow flew back to her house. She was about to put it in a mug of cider, when she stopped. She could do this at any time, she still had more fart powder in her cupboard. But, a really mischievous idea had just occurred to her.
She thought it would be funny to give this to Rarity and make her fart all day.
...
Rainbow explained her plan to Pinkie Pie, who was equally amused, and baked Rarity's favorite cake, putting fart powder in the cake and the frosting. Rainbow Dash got a cup of cider and poured the rest of the fart powder into it. It was tasteless so Rarity would never suspect.
...
Rarity was at Carousel Boutique, admiring an outfit she had picked out for a fashion show that Photo Finish would be photographing in Manehattan. This outfit was a skintight, sparkly blue jumpsuit.
Rarity heard the doorbell ring, and opened it.
"Hi Rarity!" said Pinkie Pie. "Guess what? I just made this cake for you!"
"And some cider to wash it down," said Rainbow Dash.
"What's the occasion?" said Rarity.
"Just Random Give A Cake To Rarity Day," said Pinkie.
"Why, thank you," said Rarity.
As soon as she closed the door, Rainbow and Pinkie chuckled to each other.
...
Ten minutes after Rarity had eaten the entire cake and drank the cup of cider, she put her outfit on, as it was almost time to catch her train to Manehattan.
As she admired her outfit in the mirror, Rarity's stomach began gurgling. She wasn't sure why, she had just eaten a whole cake.
As she made her way to the train, the gurgling got more intense, and she felt a pressure in her bowels like nothing before.
She was used to holding it in often, but this was a lot bigger than the occasional, unavoidable fart. Although, she was sure that was all she had to do. Not that it would be any more pleasant to fart in the middle of Ponyville.
As Rarity got closer to the train station, the pressure became more intense. She decided to quietly let it out and hope no other ponies got close enough to smell it. She stopped running, lifted her leg slightly, and let out a silent fart. She felt so relieved she couldn't help but sigh, but... this fart went on for 13 seconds.
Once she was done, she could smell the fart clearly. Fortunately there were no ponies close enough to her, so she continued on her way.
Rarity's moment of relief was short-lived, for she felt another fart coming. She held it for most of the trip, but just as she reached the train station...
PPPPRRRRRT!
Rarity let out a short, but very loud fart. She blushed beet red as a few ponies laughed at her. She giggled nervously, and boarded the train.
She found a seat in a train car and sat down, still feeling very gassy. As the train began to move, she held it in, sweating from the effort. There was no one inside this car at the moment, but if someone were to enter and smell her flatulence, it would be really embarrassing.
As the train got near Manehattan, Rarity decided to let it out so she wouldn't fart during the fashion show. She stood up and raised her behind in the air.
PPPPPPPPPPFFFFFFFFFFFFRRRRRRRRRRRRRRRRRRT!
Rarity sighed in relief as she let out a very loud fart for 22 seconds. She didn't know she could fart so loud. What had she eaten to make her so gassy? The answer came to her immediately as she farted again for five seconds. Rainbow Dash and Pinkie Pie must have put fart powder in her cake and cider. Oh, she was going to get them back for this!
...
Rarity was feeling the pressure grow as she was in line for the fashion show. Some of the outfits looked as lovely as hers, and she was nervous that she might lose. Or that she might embarrass herself onstage. She accidentally let out an airy fart, and was relieved that no one noticed.
Finally, it was her turn to go onstage. She walked onto the stage and posed for the camera.
Until, she got into the wrong position.
FFFFFFFFFFFRRRRRRRRRRRRRRT!
Rarity blushed as she farted loudly for seven seconds. Then, after this fart, came an even louder one, which lasted 28 seconds. Though the relief felt amazing, it was extremely embarrassing. The audience burst into laughter, and Rarity ran offstage.
Rainbow Dash was watching near the back of the audience, and was laughing as loud as any of the other ponies. She couldn't think of anything funnier than Rarity farting so loud for so long. She wished Pinkie Pie was here to see this.
"Who'd have thought such a beautiful mare could fart like that?" said one of the judges.
"Remember, we're here to focus on their outfits," said another judge, who, despite this, was barely able to keep from laughing.
Two of the other contestants were disgusted, but the rest were amused, and one was laughing so hard she almost peed herself.
"I don't think we'll have to worry about her beating us," said Suri Polomare, stifling her chuckles at her rival's humiliation.
"If she loses because of that it'd be a real shame," said one of the other contestants. "I think it was really funny, and she must have been holding it in for a long time."
Rarity only stayed around to see who the winner was, standing to the side of the stage trying to keep out of sight. There was no way she could win after her unladylike performance.
However, farting was not against any of the rules.
"The winner is, Rarity!" said the announcer.
Rarity was surprised, accidentally letting a short fart, and walked onstage to claim her trophy. The audience was cheering and clapping for her, Rainbow Dash among them. Suri threw her outfit in the trash and walked away, looking sour.
"Your outfit is truly lovely," said the announcer.
"Why thank you," said Rarity, before she accidentally farted again for 11 seconds.
"Even if you fart a lot," said the announcer, and the audience laughed again. Rarity blushed.
...
Rarity farted three more times on the train back to Ponyville, and when she reached Carousel Boutique, she took her outfit off. It smelled of farts, but she hoped she'd be able to wash the smell out. After all, a few of her outfits had gotten dirtier than this.
Now was the time for a party with Celestia at Twilight's castle to celebrate the anniversary of the defeat of Tirek, and the creation of the castle.
But first, Rarity let out a series of loud farts, some of which were short, and some of which were 10-20 seconds long. She had to admit the relief felt good, as unladylike as this was, and no one was around to hear it so she could fart as loud as she wanted, hoping her gas would be gone when she got to the party.
...
Celestia brought a cake over big enough for her, Spike, Starlight, and all the Main 6. Rarity was sure this one didn't contain fart powder, so she took a slice of it. She was still ridiculously gassy, and was trying her hardest to hold it in, sweating profusely.
"Are you all right Rarity?" said Fluttershy.
"I'm fine," said Rarity, hiding any signs of discomfort while Rainbow Dash and Pinkie Pie giggled. Rarity glared at them, and they fell silent.
Once the cake was done, they sat around in a circle, telling stories of things that happened in their lives since they last talked or wrote to Celestia.
"And what about you, Rarity?" said Celestia.
"Well, I won first prize in a fashion show," said Rarity, still sweating from holding in her farts.
"Anything else of interest?"
"Maybe I can write to you about it. I'm not feeling so-"
PPPPPPPPPPPPPPPFFFFFFFFFFFFRRRRRRRRRRRRRT!
Rarity farted loudly for 29 seconds. Only five seconds into the fart, Rainbow Dash and Pinkie Pie began laughing hard. Once Rarity was done farting, she blushed and giggled nervously. She had never been so embarrassed in her life. Not only had she farted so ridiculously loud and long onstage at a fashion show, but now in front of all her friends and Princess Celestia.
"I'm so sorry," said Twilight. "I'm sure she didn't mean to. She's usually so..."
"It's quite all right," said Celestia. "I don't mind. Just between us, sometimes I get really gassy too, and I think it's funny."
"You do?" said Twilight. She let out a loud fart, and blushed, giggling nervously. She could not believe she had just done that. Celestia just chuckled a bit.
"Rainbow Dash, Pinkie Pie," said Rarity. "Did you put something in my cake and my cider by any chance?"
Rainbow and Pinkie's nervous giggling explained it all. They were both in on it.
"I knew it!"
"Hey, it wasn't just us!" said Rainbow. "Starlight enhanced the fart powder!"
"Rarity, I swear I had no idea she was going to use it on you," said Starlight. "She always had me do it so she and Pinkie could fart more. I didn't know she'd use it for a prank."
"I believe you," said Rarity. "And you don't have to stop doing... that, as long as Rainbow and Pinkie are away from me for... that. Because I don't think they're ever going to pull this prank on me again." She turned around so that her butt was in Rainbow Dash and Pinkie Pie's faces. Rainbow and Pinkie cringed.
BBBBBBBBBBBBRRRRRRRRRRRRRRRAAAAAAAAAAAAAAAAAAAAAAAAAP!
Rarity farted in their faces for 37 seconds. Rainbow and Pinkie nearly fainted from the stench, their manes blown back from the force of the fart.
"Now we're even," said Rarity, who felt immense relief from this fart, and satisfaction at her revenge, having used their own prank against them. She didn't even care that she had just let out the longest, loudest fart of her entire life in front of everyone.
Spike and the other ponies laughed, including Celestia, and Twilight opened the window to air out the room. Rainbow and Pinkie apologized for pulling this prank on Rarity, who found it in her heart to forgive them in exchange for the promise to never do it again. They quickly agreed to this, not wanting Rarity to fart on them like that again.
Then they got back to the party, but Rarity farted a few more times. Rainbow Dash and Pinkie Pie smelled like farts for the rest of the day, but it was only noticeable if they got really close to them. Despite her humiliation, Rarity was able to have some fun. Maybe it was what Celestia had said. Maybe it was the fact that she had won the fashion show anyway. Maybe it was her revenge on the ponies who caused her gassiness. Or maybe some part of her secretly thought it was fun to fart.
Most likely, it was all of the above.
Her farting subsided by the end of the party. Despite feeling better about it, she still felt a little embarrassed. When Fluttershy and Applejack noticed this, they gave her a hug and said they still loved her, and Celestia said she didn't need to feel ashamed.
Nevertheless, it was two days before she fully got over it, and three days before Rainbow Dash and Pinkie Pie had another farting contest.