"Aw, you were so cute Luna!" said mare Celestia, looking up at filly Luna standing on her chest, her eyes half-lidded. Filly Luna leaned down and kissed her older, older sister on the mouth, both their eyes closing.
"What do you mean, 'were?' I'm still–" Mare Luna was cut off by filly Celestia, who sat her little ass down on her big little-sister's face, her smug expression replaced by a wide-eyed blush when mare Luna started to dig into her tiny asshole with her big horse-tongue.
Filly Luna pulled out of her kiss with mare Celestia, a bridge of spit briefly drawn between their mouths before snapping.
"How's it going, sis?" said filly Luna to filly Celestia, who gave her a wink before moaning loudly, her tongue lolling as she covered mare Luna in glittery fluid.
"I just... Came on your face." managed filly Celestia. "So you have that to look forward to, however many years from now."
"Aw, gross." laughed filly Luna, turning around and planting her rump on mare Celestia's face. "You better get ready for the same." she said.
Filly Celestia licked her lips as her little sister rode up and down on her future self's face, making a mental note to dig deep into her pussy.
"Hey little, er, big Luna." said filly Celestia. Go get on big me and make out with yourself."
Mare Luna wasn't sure how she felt about being bossed around by her little big-sister, but she did want to see what it was like to kiss herself. She scooped up filly Celestia in her hooves and rolled over, using her wings to fly over mare Celestia's upturned legs and settle down, her butt cheeks resting on mare Celestia's teats.
"Hey, what are you–" filly Celestia was cut off when mare Luna pressed her against filly Luna, the two locking lips. A new memory surfaced then in mare Luna's mind, showing her the absurd amount of tongue the two fillies were playing with. She remembered that she practically tried to swallow her sister's, and how she felt the ribbed-roof of her mouth which broke the kiss, watching as it happened with a feeling like deja-vu.
"Ah!" cried filly Celestia. "That tickled!"
Mare Luna set filly Celestia aside, finally going in to taste herself.
"Hey!" cried her littler sister, before she remembered that this was what she wanted: to watch her sister (sisters?) make out with herself on top of her.
Mare Luna dragged her tongue all over her younger-self's face, all the while the little moon-princess shivered and came multiple times on mare Celestia.
Mare Luna leaned back and as she did pulled filly Luna's head down to her own teats, encouraging her to suck them and letting mare Celestia come up for air.
After a gasp and some heavy breathing, mare Celestia brushed filly Luna's tail away and craned her neck forward, tonguing the tiny teats between her younger sister's legs.
All the while, filly Celestia stirred her privates with her hoof, enjoying the show.
Then the door flew open and Twilight Sparkle came in. "Princess! There's a problem! A time paradox..."
Twilight was stunned by the scene playing out before her. The only one really able to notice her intrusion was filly Celestia.
"Who are you?" she said, halting her masturbation to examine the interloper.
"Wha– I'm Twilight Sparkle, Celestia's apprentice. Who are you?" said Twilight, her mind working overtime to process what she had encountered.
"Woah, you're my apprentice?" said filly Celestia, using her magic to close the door behind Twilight and pull her onto the bed.
"Kiss me." said filly Celestia. "That way, I'll remember to pick you when the time comes."
Twilight was dumbfounded, but managed to piece together the conclusion that the paradox was right before her before she became a part of it, her lips suddenly pulled against her mentor's childhood lips.
Filly Luna came again on mare Celestia's face, and mare Luna came on her teats while Twilight watched out of the corner of her eye.
"Oh, Twilight. I didn't see you there." said mare Celestia, wiping the glittery fluid from her lips. "You probably realized by now that this is how we first met." she said. "Well, from my perspective, anyway."
Twilight's mind exploded, and she felt like she was just sifting through the pieces.
Filly Celestia pushed her on her back then and started licking her pussy while Twilight just sat there, her eyes glazed-over.
"Is she gonna be alright?" asked filly Luna, and Celestia replied.
"She will be fine, but she needs our help to break free of her mind-prison. Everyone, let's show her a good time."
The four ponies descended on Twilight like scavenger birds, tonguing her ears, sucking her horn and ramming their horns into her ass and pussy until glittery pony-girl fluid squirted out of her pussy like water from an over-pressurized drinking fountain.
Then they doubled down, making out with each other now and again, and sucking pussy-juice from each-other and transferring it to Twilight's mouth via kiss.
Filly Luna began licking the bottoms of Twilight's rear hooves while mare Luna took the front ones, fitting them into her mouth and pressing the bed of her warm tongue against the sole.
Mare Celestia nuzzled and kissed Twilight's neck, while filly Celestia suckled on her older self's teats.
Twilight came multiple times, her eyes rolling back into her head. When they came back her pupils narrowed slightly and she began to regain focus. For a brief moment she saw four ponies standing over her, but when she blinked there were only two: Celestia and Luna.
"What... What happened?" she said, sitting up.
The sisters looked at each-other, blushed, then back to Twilight.
"Well, you came into my bedroom to warn us of something..." began Luna, her eyes darting to the side as she trailed off.
It was just the three of them then. Twilight was sure there were more a moment ago, but she only recalled the sisters.
Author's Note
I wrote this all in one in one go. Hopefully it isn’t too weird, and doesn’t have too many errors. I was in a zone and wanted to use the motivation before it faded away. 
