You feel like you've been pinned under Applebloom's rear for hours, the smell and lack of oxygen makes you lightheaded, but every time you think you're passing into blissful unconsciousness, you filly dominatrix feels your breathing slow and kicks you in the ribs to keep you awak.
"Ah can't get mah Cutie Mark fer mah farts unless yer awake to sniff 'em! Now get a whiff a this!"
She rubs her sweaty buttcrack up against your nose a few times, before letting a high-pitched squeaker rip out. Then, she expectantly checks her flank, finding it to still be blank. She puffs out her cheeks in frustration, forcing out another poot. You're too weak to struggle any more, but your nostrils burn ferociously from the stink. Just as she pushes another gust out, you hear hoofsteps. Out of the corner of your eye, you can see two other fillies, a unicorn and a pegasus.
"Hey Scootaloo, hey Sweetie Belle! Did Spike give ya'll mah message?" Applebloom says, rising off of you. You immediately think to get up, but those farts must have sapped every ounce of your strength, you can't even manage to lift your neck up.
"Hey Applebloom," The pegasus, Scootaloo, says "We got your message, but why did you ask us to eat a whole buncha veggies?"
"It was Sweetie Belle's idea!" Applebloom says, "I'm gonna get us our Cutie Marks for fart torture. Right Sweetie Belle?"
"Yeah, look!" Sweetie Belle says, pulling some sort of device from her saddlebags, "I saw my sister Rarity doing it, she's a real pro! She called it epr-.. Epra-...Uhh.."
"Eproctophilia?" Scootaloo chimes in.
"Yeah, that! She uses this thingie here, see it's supposed to fit around a stallion's muzzle, and ya stick your butt around these nozzles here, and all the gas gets trapped inside the mask's nose."
Applebloom picks up one of the nozzles and looks at it quizzically, "Are you sure this thing works? Ah was just fartin' on that pony other there's face and it worked just fine."
"No, look," Sweetie says, "Rarity has Big MacIntosh over sometimes, and she eats a big dinner of cabbage and this skunky beer, then she and Big MacIntosh go into their room, I saw 'cause I hid in the air vents, and Rarity puts this tube in her butt and puts the mask on Big Mac's face, then she farts in it and Big Mac's wiener gets all stiff and big, then she puts it in her mouth and sucks on it until he pees white all over her!"
"But Sweetie Belle, this pony doesn't have a wiener, she's a girl."
"Oh." Sweetie Belle says, looking disappointed, "Can we do it anyway?"
"Sure!" The other two say in unison. They rush you, strapping a leather gasmask around your face. The thing is tight, and already reeks of something fierce, not to mention the eyes of it are so scraped and stained that you can't see anything except for what's rich in front of you. But you can hear those three fillies talking,
"Ow! Sweetie Belle, watch how deep ya put that thing, yer gonna get poop all over it, and Rarity'll kill us!"
"Sorry! But, I don't think she'll notice..."
"Hey, is my tube in far enough?"
"Looks good to me Scootaloo."
"Hey Sweetie Belle when do we start?"
"I already started."
You smell something awful rush into the mask, Sweetie Belle's fart. God, what did she eat? Another smell washes over you, and another, they all must have started farting now, creating a steamy sauna of gas. You feel like you're buried under a mound of rotting trash. It must be some sort of testament to their friendship, together they smell worse than anything else in the world! You slowly feel yourself succumbing to the smell of their fetid bowels...