Author's Notes:

Done by request, and needless to say, ponies this time.

Also, I continue to portray Lightning Dust differently than in the show because I've already done it this story with her human counterpart.

In Equestria, Rainbow Dash was very much like her human counterpart. She only washed once every two weeks, and therefore she smelled worse than the ponies' farts. And ponies were known for farting a lot, although Rarity would often fart silently if she could, wanting to seem more ladylike, although Celestia would sometimes fart in front of them. Fluttershy would always fart silently, as if she didn't even know how to fart loud.

A difference was that Rainbow Dash's boyfriend was Soarin. They were currently spending the night together, having just flown around Ponyville for fun.

"What should we do now?" said Rainbow Dash once they were back in her house.

Soarin sniffed her. "How about we have a little fun here?"

Rainbow Dash knew what he meant and chuckled. "Where do you want to sniff first?"

"The usual." Soarin sniffed Rainbow Dash's armpits. He had a thing for smelly mares and Rainbow Dash fit this perfectly. Luckily for him, she was attracted to him as well. She loved it when he sniffed her. Rarity was disgusted at her stench but put up with it with her perfume and air freshener. Rainbow Dash was also sure Rarity would sometimes take advantage of her smell by farting silently in front of her, as the smell of her farts would be drowned out by that of Rainbow Dash. Of course it was always funny for her whenever Rarity accidentally farted loudly, but she was less embarrassed about it than her human counterpart would be because most ponies farted in front of each other all the time.

Soarin finished sniffing Rainbow Dash's armpit. "I can never get enough of that smell. What next?"

Rainbow Dash lay down and raised her back legs so her back hooves were in the air. Soarin sniffed them. They smelled just as bad as her armpits, and he loved it. Of course she washed her front hooves often.

When he was done he tickled her smelly hooves a bit.

Rainbow Dash laughed. "Stop it!"

He tickled her for about ten seconds before he stopped. Rainbow stood up and turned so she was facing away from him, raising her rear end slightly in the air.

Soarin walked over to her butt and started to caress it with his hooves, all the while smelling it. Rainbow Dash's butt smelled only slightly better than her armpits and hooves.

Rainbow Dash sighed with pleasure. All ponies loved getting slapped in the butt, but Rainbow Dash loved a butt massage even more. And she knew Soarin loved it as much as she did.

He was rubbing and sniffing her tush for five minutes when she farted loudly.

FFFFFFRRRRRRRRRT!

Rainbow Dash chuckled, while Soarin inhaled deeply. He loved it when she farted in his face, and didn't mind the smell, because it didn't smell as bad as her. He might have even liked it if her farts smelled worse than her.

After about a half-hour of butt-rubbing and non-stop farting, Rainbow Dash and Soarin lay down in bed and went to sleep.

...

The next day, Rainbow Dash met up with her friends, who were going to cheer her on in an aerial race she would be competing in. Rainbow Dash wore a pair of smelly skintight black shorts and a blue T-shirt the same color of blue as her mane. She wore this for almost all her performances and never washed them, so they smelled as bad as she did. Plus, once she had forgotten to use the bathroom during a race and ended up peeing herself, and hadn't washed her shorts then either. So they smelled a little like pee as well.

Her friends gave her their usual words of encouragement.

"And remember, darling," said Rarity. "Even if you don't win, we'll still love you." She sniffed Rainbow Dash and recoiled. "Phew. You really need a bath."

"Fine, if Lightning Dust beats me, I'll let you give me a bath."

"Deal." They never set a condition for Rarity in the bet, otherwise she might cheer for Rainbow Dash to lose. Even though it was clear Rarity wanted to give Rainbow Dash a bath.

Rarity let out a long, silent fart, then she and the other ponies moved to the audience as Rainbow Dash met up with her opponents.

Lightning Dust was wearing a black and green jumpsuit, as she always did in her performances, which weren't just limited to races.

"This time I know I'm gonna win," said Lightning Dust.

"Wanna bet?" said Rainbow Dash.

Lightning Dust sniffed Rainbow Dash and recoiled. "If I win, you have to pee in your shorts again!"

"And if I win, you have to go in the closet with me for an hour."

"Deal!" They spit on their hooves and did a fist bump.

BBBBBBRRRRRRRRRRT!

PPPPPPFFFFFFFFFFFFFT!

Rainbow Dash and Lightning Dust chuckled as they let loose with a flurry of explosive farts. They stopped farting once they reached the starting line.

"On your marks... get set... go!"

Rainbow Dash and Lightning Dust flew ahead of the ponies. Lightning Dust was flying behind Rainbow Dash, but she could catch a whiff of her so she flew to the side. There, she was clear of Rainbow Dash's odor. They flew neck in neck, still farting every few seconds.

As they were about to finish their final lap, Rainbow Dash pulled ahead and crossed the finish line.

"Rainbow Dash wins!" said the announcer.

"Oh no..." Lightning Dust sat down after crossing the finish line second. "I gotta go into the closet with Rainbow Dash now..." A long, deep-pitched fart made its way out of her.

"Congratulations, Rainbow Dash!" said Twilight Sparkle.

"We knew you'd blow them all away!" said Pinkie Pie.

"Yes, that was quite an impressive finish," said Rarity, wanting to be polite but a little disappointed she couldn't give Rainbow Dash a bath.

Rainbow Dash drank from her water bottle. "Come with me, Lightning Dust."

"Wait!" Lightning Dust drained a two-liter bottle of soda in seconds. "All right. I'm as ready as I'll be."

Rainbow Dash led Lightning Dust to her house, and the other ponies went home as well. Once everyone was gone, Rarity let out a loud fart, and sighed of relief.

After arrival, Rainbow paused to get another drink of water. Lightning Dust thought this might not be so bad after all. She could test how long she could handle Rainbow Dash's smell for, and if things got out of hand, she could fart and hopefully that would make Rainbow's smell less noticeable to her.

They got into the closet, and Rainbow closed the door.

Soon the closet became full of Rainbow Dash's smell. Lightning Dust had never smelled anything more foul in her life. After sniffing for a bit, she breathed through her mouth to avoid the foul stench. Though every few minutes her mouth would get a little dry and she'd have to breathe through her nostrils again, and as she did she smelled the horrible smell that was coming from Rainbow Dash.

And, she soon realized her gas was gone and she wouldn't be farting anytime soon. It would always come and go with ponies. They'd fart a lot and then not fart at all for a while.

Twenty minutes in, Lightning Dust said "Can we take a break for a minute? I have to go to the bathroom."

"You should have gone before we came in," said Rainbow Dash. "And maybe not drank a whole bottle of soda. Besides, how do I know you're not gonna try to escape?"

Lightning Dust moaned and fidgeted where she sat. Smelling Rainbow Dash didn't help, but maybe this could also test her limit on how long she could hold it under these situations.

Ten minutes later, Rainbow Dash stood up and positioned her rump right in front of Lightning Dust's face. She didn't fart, but Lightning Dust could smell her much more closely. Not that it was much stinkier than the room was now, but Lightning Dust was having enough trouble with the smell and her desperation as it was.

"Stop!" said Lightning Dust. "I need to pee!"

"Oh, all right." Rainbow Dash moved a bit away from her, then, with a smirk, she put her armpit next to Lightning's face.

"Ugh!" Lightning Dust leaked a little and Rainbow resumed her original position, chuckling.

Only four uncomfortable minutes later, Lightning Dust started to pee in her jumpsuit uncontrollably. She blushed beet red and whimpered. Rainbow Dash chuckled.

"This is the last time I'm doing a bet like this again," moaned Lightning Dust as she finished peeing.

Lightning Dust sat in her wet jumpsuit in the closet full of Rainbow Dash's smell, until the hour was up. As soon as Rainbow Dash's alarm went off, Lightning Dust opened the closet and ran out, taking deep breaths of fresh air.

"Congratulations on not fainting," said Rainbow Dash.

"You know," said Lightning Dust, "maybe I should become a smelly pony too. Then I'll be able to stand your smell. How often do you wash?"

"Once every two weeks, and without soap."

"Then that's how I'll wash too!"

"I look forward to it." They did a hoof bump.

"And I won't wash this outfit again either."

...

Next, Rainbow Dash met up with Applejack, as they were going to race on foot.

"Howdy, Rainbow Dash," said Applejack. "How'd the Lightning Dust closet bet go?"

"It was awesome!" said Rainbow Dash. "Lightning Dust wet herself, and she's going to become as smelly as me."

"Sounds like fun." Applejack sniffed Rainbow Dash and recoiled. "Yup, you still smell twice as bad as me!"

Applejack tied Rainbow Dash's wings, getting quite a few whiffs of her as she did.

"Is this really necessary?" said Rainbow Dash. "I told you I won't use my wings in our competitions anymore."

"Just makin' sure."

Rainbow Dash farted loudly, and they got into position and started running. Rainbow Dash was running ahead, but Applejack made sure not to run directly downwind of her, and soon caught up to her.

Applejack won this race, and she and Rainbow Dash did a hoof bump. Applejack wrinkled her nose as she untied Rainbow Dash's wings.

"Good thing I didn't bet with Rarity on that one," said Rainbow Dash. "Otherwise she'd give me a bath."

"You really need one," chuckled Applejack.

"I can't wait till our next race. See ya!" Rainbow Dash flew toward Pinkie Pie's house, having held in the rest of her farts during the race because she and Pinkie would be having a farting contest.