Not my story, just reposting from a long time ago.
>"Okay Anon, be sure to hold on tight to my legs now..."
"You know it."
>You are on the roof of Sugarcube Corner with your best pranking buddy, Thingpone.
>You firmly grasp her hind hooves.
>She helps out by growing some tendrils from her withers which wrap around your wrists.
>Her plot grows a face that looks at you sternly.
>"I mean it, Anon, hold on!"
"Okay, it won't be like last time, I Pinkie promise. Geez."
>As her body elongates, the secondary butt-face disappears except for one eye on a stalk.
>A tentacle emerges, points at the eye, then points at you.
>Thingpone's body stretches longer, and longer.
>Her entire anatomy becomes distorted, her forelegs becoming pseudopods with small toothy mouths on the end.
>One of them grows another eye.
>Mrs. Cake had set a pie out to cool on the window sill.
>"Just a little further..."
>The toothy pseudopods latch onto the pie plate.
"Whoa, Thingpone, that was kinda loud."
>And it has attracted attention.
>Lily, passing by at this opportune juncture, hears Thingpone's cry of triumph.
>Thingpone, in elongating, has abandoned most of her pony form.
>There is a long, ropy tube of raw flesh, with bones and viscera sticking out at odd angles, hanging from the roof of Sugarcube Corner.
>Lily gasps and points, "THE HORROR!! THE HORROR!!"
"Jig's up, Thing!!"
>A horrified crowd gathers as Thingpone, still clinging to the pie, retracts up the side of the building to you.
>You grab the pie from her as soon as it comes into view.
>"HEY! My pie!!!" you hear Mrs. Cake cry out.
"Time to go, Thingpone! Plan B!"
>Thingpone nods and climbs up on your back, securing herself in place with thick, muscular tentacles.
>She sprouts bat wings.
>You run towards the roof's edge and leap off.
>Thingpone's wings fill with air, and you soar away together, clutching the pie.
"HA HA HA HA HA!!! Later fagets!!!"
>The ponies in the square below rage.