>"Can we get this over with already, sister?"
>Celestia, sprawled out over the crumb-laden carpet of Luna's bedroom, watched her sibling with a disapproving scowl.
>For the younger princess' daily gaming session everything had to be just right. 
>Her bowl had to be adequately filled with chips.
>Her pizza had to be just as hot and melty as she liked it.
>And the curtains had to be drawn to keep any pesky daylight from distracting her. 
>Mostly, though, she was just savoring every glorious second of her victory.
>Her bets with Celestia often ended in defeat and a faceful of gnarly solar winds, but this time was different.
>For once in over one thousand years, thanks to a trivial bet on how Twilight Sparkle would sign off her weekly friendship report, Luna had won.
>This was her prize.
>"Now, now, Tia. I don't want to rush things. Getting a new gaming chair is serious business!" 
>Luna gave a girlish giggle, hopping towards her older sister.
>Only now did Celestia look closely enough at her sibling's perky backside to realize she had on a pair of blue-and-black striped panties.
>Judging by the many stains and marks littered around their cottony surface, and the acrid stench of mare sweat and dried cumstains, this particular pair hadn't been washed in what seemed like weeks.
>Little did Celestia know, it had actually been a little over a month.
>Luna reversed herself up the length of her sister's torso, her supple rump swaying teasingly above Celestia's face, who couldn't help but gaze, almost hypnotized, by the repetitive motion of Luna's ass swinging back and forth as it loomed closer.
>Celestia held her breath.
>With a light thump, Luna's rear dropped down onto the side of her older sister's face.
>"Ahhh! There! Quite a snug fit, Tia, wouldn't you say?"
>A grumble of disapproval was all Luna got in response.
>Even if Celestia had wanted to say more, the noxious smell of sweaty horse ass had her deliberately keeping her lips sealed. 
>Celestia wasn't sure what Luna had been doing prior to this session, but whatever it was had worked up quite a sweat.
>She could feel the moisture seeping into her fur with every grinding, swivelling motion of Luna's hips. 
>Her nostrils flared. Tears already pooled in her eyes at the vulgar scent, which just seemed to get worse with every passing breath.
>"Now, just to ensure you don't try and weasel out of your punishment..."
>Celestia's body tingled.
>Deep blue magic sparkled across her skin, freezing her muscles like stone to keep her in place.
>"L-Luna!"
>"Just a precaution, sister!" She smirked.
>The TV blinked into life, casting a blinding blue hue over the sordid scene of the younger princess riding her sister's face like a bike seat.
>With her magic she picked up a generous portion of cheesy puffs and tossed them all into her gob, washing down the artificial cheddar flavor with a swig of cheap sugary energy drink.
>The sounds of gunfire and teammate chatter could be heard filtering through Luna's headset.
>This was followed by a wispy gurgle from her stomach; a confirmation to Celestia that as bad as the smell was right now, it could only get worse.
>Stewing down there under Luna's musky moons, she noted to herself that the alicorn's haunches seemed plumper than usual.
>She could feel a padding of fat pressing into her snout.
>Still firm and tight, but with enough pudge to give a bit of bounce whenever Luna jostled around.
>If she didn't know any better she'd swear her sister had been fattening up on purpose.
>With the way she was shovelling pizza and snacks down her throat it was no wonder she'd put on weight.
>At this rate she would soon be catching up to her older sister in the trunk department.
>Just as Celestia was starting to get used to the wholly unpleasant feeling of her own sister's ass smothering her face, Luna spoke up to confirm things were about to go from bad to worse.
>"Wouldn't you know it, sister, I believe I need to let one loose! Whenever I get a new gaming chair it's customary to break it in a little, and there's no time like the present!"
>With only this as a warning, Luna lifted a cushy cheek from Celestia's muzzle and grunted, funnelling a torrent of thick, bubbling filth directly into her nostrils.
>Even with the panties there to partly buffer the blow, Celestia could feel a sickly current of greasy air washing over her face.
>With a sigh, Luna settled back down, trapping her with the fresh stink.
>And what a stink it was.
>Celestia's entire body convulsed after the briefest of whiffs, at least as much as the restrictive spell would allow.
>Luna's poor dietary decisions had stewed together a mismatched mess of fried onions, cheese, grease and rotten eggs. 
>And Celestia had just taken a hit of it direct from the source.
>As the devilish brew permeated through the room and eventually reached her, Luna's face crumpled up in disgust.
>Her own brand was often foul, but the stench she was putting out today was worse than usual.
>Using her wings, she wafted the hot funk away from her face and back down towards her sister's, tensing out another quick rumble of gas to stoke the flames of disgust roiling in her sibling's senses down below.
>"Utterly repugnant!" Luna chuckled, slurping the mozzarella from a slice of pizza before rolling the base up and stuffing it down her gullet.
>Using a week-old half eaten hayburger she wiped some of the food stains from around her lips.
>And, after eyeing the rancid sandwich for a moment, stuffed that into her maw as well.
>Her stomach groaned in protest at having such a putrid mixture of food cast into it.
>But in response to this Luna merely slapped her full belly and laughed.
>Celestia, however, was not finding this situation nearly as humorous as her sister.
>She was much more focused on surviving the waves of torrid stink.
>It were as if Luna had been holding her rips in all day for this very moment, and now Celestia was getting the absolute fury of a whole day's worth of fermented fast food blown into her face over and over again.
>With any luck, the intensity of the gas would soon knock her out. That wouldn't stop Luna from pumping out her fumes of course, but this punishment would be a lot easier to take unconscious.
>Sadly for Celestia, she would have no such luck. 
>Just as Luna could feel her sister's struggles dying down beneath her, she stood, using her controller to fan her stinky tush with a sigh.
>"Round one and you're still breathing, sister. Color me impressed. It's only going to get harder from here on out, though. I had jalapeno poppers for lunch so this next batch is really going to sting!"
>The pride with which Luna talked about her appalling diet absolutely disgusted Celestia, almost as much as the rippling explosion of ass that greeted her the moment her sister slammed herself back down.
>Celestia's lungs cried out for air; with the windows locked shut and the thick curtains drawn, the air in the room was like a murky soup of sweat, pizza, and farts. 
>And just to add even more to it, Luna's ass tilted to one side and gusted out a long, hissing plume of junky gas.
>This time there was a nasty undertone of rotten jalapenos and oily, spoiled cheese sauce.
>Luna eased herself forward as her monstrous steamer of a fart picked up some audio, turning from a hiss to a squeal, ruffling her panties and threatening to singe a hole right through the middle of them.
>"Oh, stars..." The princess of the night groaned with relief, feeling her netherlips glisten and stamp a new stain into the front of her panties.
>After ten more seconds of windy release, her ass finally silenced and she got comfortable on Celestia's face once more.
>The older sister gagged into the mask of fart-stained cotton over her mouth.
>Now she could actually TASTE her sister's flatulence as well as smell it.
>"Oh, I'm just getting started, sister! I'm a roll this match so don't expect this to end anytime soon."
>Celestia burbled.
>"But you're doing such a fine job that I wouldn't want to move even if I was losing! Perhaps I should shapeshift you into a pair of panties! That way I can have you riding up my sweaty crack all day long as I go about my duties! What say you to that, hmm?"
>Her butt lifted slightly to let Celestia answer.
>But as soon as her sister opened her mouth to respond, a gust of wet flatus fired into it with a trumpeting blare.
>"That's what I thought!"
>Celestia's eyes rolled into her head.
>This was the last time she would wage a bet with her sister.