A hushed silence fell in the cave - some 300-odd creatures stood stock still, staring up at the mare on the make-shift stage. A good half of the crowd is ponies, but alongside them is a myriad of other creatures - kirins, changelings, yaks, even a dragon. On the stage, the pink mare prepares her sermon.
"Today we celebrate the gifts of our bodies - Taste and Touch, Sound and Smell! Oh, and Sight!" She giggles. "We celebrate the successful harvest of our lord's greatest gift - the squiggleshroom!" From behind her, two massive yaks step fourth pulling carts full to the brim with shimmering blue mushrooms, and the crowd collectively gasps. "Today we merge our souls with our bodies, temporarily, as a sneak peak into what life will look like upon our lord's return - When he brings us the Ever-Party!"
The crowd bursts out into cheers, and the pink mare squeals with delight. She begins tossing mushrooms into the crowd, stuffing a few into her mouth as she does so, and grins so wide she feels like her cheeks might burst.
"Feast, Fuck, and have Fun! Chaos awaits!" She shouts as she dives into the crowd.
Just six moons ago Pinkie Pie was a depressed mare living on her family's rock farm. Her lot in life was simple, bland, and tedious. Eventually, it all got to be too much for her, and she snuck out in the middle of the night - only her closest sister Maud knew she was leaving.
Pinkie has always been different - from her bright colors to her short attention span, she never fit in at all back home. And once she started showing signs of being...well, chaotic, she was kicked out of church, and became a stain on her parents good name. Her ticks, her future-telling, her occasional ability to teleport - she's no ordinary mare. All she ever wanted was to be celebrated for her differences. She has nothing against the church, really! It's just that they seem to think her to be a demon. Pinkie just couldn't stand to see her father be so disappointed in her.
The open road was hard for Pinkie Pie, but not harder than a life pushing rocks uphill. She was chased out of several towns, eventually settling in Ponyville as an apprentice baker - before getting promptly thrown out again when she got excited and popped out of a cake. She hopes the town isn't giving the cake family too much trouble for standing up for her...
So into the Big Scary Forest she went, steering clear of the big old temple that resided on the edge. She met what she thought at first was a very strange pony, then found out was a zebra - and the Zebra named Zecora gave her a squiggleshroom, telling her it was her destiny.
Pinkie did laugh at that, though she felt rude afterwards. Common ponies don't get to have destinies, silly, she had said. A pony with a destiny gets a mark - something beautiful upon their flank, proclaiming their destiny to the world. Only brave, powerful, important ponies have destinies. The zebra was amused, and told her she should try it and find out.
"Try it out, and you shall see - just how important is your destiny."
So Pinkie did, and she had the most amazing time! She swam in a chocolate river, she flew in the sky, she tumbled and stretched and changed and wiggled and wobbled - nothing was real and everything was magical and beautiful, and she got to meet Him.
Chaos Himself.
When He touched her for that first time, she felt destiny wrap its arms around her, and she got her mark. They didn't speak, not exactly, but they communicated - soul to soul - and she understood everything and nothing all at once. She and her chaotic magic have big things to do...
Pinkie Pie settles onto her back on a large table pressed against a wall of the cave. A changeling is between her legs, eating her out with unrestrained fervor, his tongue thick and rough inside her. It changes constantly, pulsing and sometimes duplicating inside of her, never the same shape for more than a moment. She stuffs hooffull after hooffull of cake into her mouth, caring little for the mess of frosting in her mane. The mushrooms are starting to hit her, and her body tingles pleasantly all over - she cums immediately as she feels the effects starting to take control of her mind, squirting all over the face of the changeling. Something hard enters her mouth - a body part of some kind - and thrusts into the mess of cake and saliva. Pinkie chokes on the intrusion, but doesn't mind. All things are good things now.
Pinkie Pie feels a hoof caress her cheek, and opens her eyes to see Zecora sitting beside her, smiling down at her. Pinkie, unable to use her mouth for anything other than sucking and swallowing, hopes that Zecora - and her many colored, wavy stripes - can see the smile in her eyes.
Zecora never partakes in the orgies, saying she doesn't enjoy sex, but always comes by the caves to join the party anyway. Pinkie loves having her around.
Pinkie loves everything right now.
She stares blankly at the ceiling of the cave, watching lights dance and flicker. She can hear music - beautiful drums played by that white unicorn with the glasses - and she can also feel the music inside of herself. The torchlight dances across Pinkie's eyes as the cums again and again, just now noticing that the changeling is gone and there's a pegasus between her legs now. Oh, and her mouth is free, though filled with sticky semen-frosting mix. She gulps that down and takes a deep breath of air, marveling at the feeling of her lungs expanding.
Above her she sees sparks, sparkles, twirling lines...Swirls of color and bubbles of understanding. She opens her mouth, and lets out a voice that is not her own.
As her Lord speaks through her, she feels true bliss, and all the creatures in the cave stop their fucking and feasting to watch her.
"Oh, such wonderful frolicking you all are doing! I simply must thank the event organizer. Oh, and here she is - " Pinkie's forelegs move on their own, shaking her own hoof as if thanking herself.
"Anywho, there are BIG things coming for Equestria soon, keep your eyes peeled-" A banana peel falls to the floor from behind one of Pinkie's eyes - "for the coming revolution. Only once the Moon is free, can I be made whole again. One part of me is in this cave, and another is right bellow Sun Butt Herself. Another is far, far away...But coming closer!
"Sorry to interrupt. Please, resume your partying."
Pinkie gasps for air, suddenly back to herself again. Even her high is gone, sobriety hitting her like a brick to the sternum. The whole room watches her with baited breath.
"Well, you heard Him! Our Lord says to Party!" She shouts at the top of her lungs, and the whole room erupts with noise. Hooves stomp, hands clap, and yak horns bang together. Pinkie looks over at Zecora and smiles, leaning over to kiss her on the cheek. "I couldn't of done any of this without you. Thank you sooooooo much!" She says as she wraps the zebra into a tight hug.
Pinkie heads back into the fray filled with excitement and determination. This odd group of creatures she's gathered is her new family - misfits and weirdo's, just like her. All committed to the cause of bringing Chaos back to Equestria, so that their party never has to end. Pinkie has never been more happy.
Author's Note
I have never written discord before so please, correct me on the characterization if it seems too abnormal 
He is a little different in this universe, but not too much different, so I'd like to hopefully get his voice right.
