Pinkie Pie discovers a new type of mushroom growing all over a forest. She tries one, and it makes her ridiculously gassy. After having Rainbow Dash try one, the two decide to have fun with it, and sneak them to some of their friends. Leading to a big farting contest between the two fart-loving females.
Contains: Fart (obviously), ridiculous unrealistic levels of it, and some brief non-descriptive instances of watersports. And sweat, if that's a thing. No scat this time, it might be too big a turn-off to anyone who would enjoy it otherwise.
If you neither have the fetish for it nor find it funny, not recommended for you. It's not meant to offend anyone who is disgusted by it, and if you are, ignore it. Also, well, you know the usual drills for my stories, don't take too seriously and don't expect much of an actual "story".
Of all my fart stories this takes it to the most extreme. And by "extreme" I mean ridiculously high levels of gassiness. I tried to make it equally appealing to the two types of people who are interested in it.