This is sort of similar to something that might happen in "Distance" or may see the light of day as a portion of another standalone fic. In the meantime I present it to you because it has Celestia and Twilight being cute so what other reason could I possibly need?
“Although the root cause of the Lunar Rebellion has been known for a millennium, many Equestrian scholars still argue over exactly how the night sister came to be so marginalized as to turn to cloaking the entire world in eternal darkness. As the historian Ponysephus pointed out, ‘it all seems to have escalated rather quickly.’ Indeed, what contemporary sources remain indicate that the Princess of the Night was well loved by her subjects, an object of both veneration and more earthly kinds of attraction. A list of those ponies who attempted to woo her would be neigh as long as this entire volume, such was her beauty.
Nonetheless Celestia was always known to be the more beloved sister, though few writers of the time were gauche enough to say so openly. There are a number of theories as to why this would be. Some scholars have put forth the theory that her decision to invite the donkeys into Equestria early in the princesses’ rein won her many admirers. Indeed, the Duke of Canterlot, Lord Nova, wrote a lengthy poem praising what he called ‘the Princess Celestia’s donkey,’ which was widely circulated at the time, though it is little known to modern scholars.
It has been noted as odd that Lord Nova’s poem referred to a singular animal, but this is believed to be metaphorical. Indeed, the donkey in the poem seems to be representative of the donkey population that settled in Equestria as a whole. The duke praises the robustness of the community by describing the metaphorical donkey as ‘firm, supple, and possessed of great power.’ He writes of the beauty of Celestia’s donkey, describing it as ‘beyond compare in the treats it brings to a pony’s eyes, so that to look upon it for too long is to go blind, and yet one could do so and feel their vision has not been lost in vain.’
Some meaning of the poem is obviously lost in the translation from Old Equuish. Many scholars do not know what to make of the latter passages detailing the duke’s apparent desire to pet the princess’ donkey. Indeed, Nova goes on at great length of his desire to ‘gently pet, fondle, and caress it.’ He describes drawing patterns in the donkey’s apparently white fur with his tongue. Towards the end of the piece he writes that if he could cuddle with Celestia’s donkey for the night, ‘truly my dreams would be the sweetest, and the morn would find me refreshed beyond measure, though I would weep that the most wonderful night of my life was over.’ Most historians agree these passages are either some kind of extended metaphor for the fondness the duke bore for Equestria’s donkey population, or a private joke between himself and the princess. Nova was known to be among Celestia’s favorites at court because of his ability to make her laugh. Oddly enough, he apparently fell out of favor for several months after this poem was circulated, which modern scholars find quite baffling.”
Twilight Sparkle’s gaze slowly rose from the the book she was reading, “A History and Analysis of the Lunar Rebellion” by Edward Horsson, to look at the princess. Celestia had been watching Twilight with a patiently bemused smile on her face as the unicorn went about her studies. Their gazes met, and Twilight’s eyebrows slowly knotted together as she looked at the princess. Celestia blinked, her smile slipping a little in confusion.
“Is there something in your studies that I can shed some light on, my faithful student?”
Twilight wordlessly lit her horn with magic and levitated two books off of their shelves and over to her desk. Celestia blinked as the unicorn opened “An Ode to Celestia’s Donkey, in the Original Equuish,” and began flipping through “The Egghead’s Guide to Translating Old Equuish to Modern Equestrian.”
After a moment Twilight’s head snapped back up to meet the princess’ eyes again, and the ghost of a smile flickered across her face.
“‘Donkey’ isn’t exactly the right translation of that word, is it?”
Celestia was, as a rule, very good at controlling visibly signs of emotion. She also had a very pale coat, which at this point was something of a liability as it did absolutely nothing to hide the deep blush that began spreading across her cheeks. Celestia failed to suppress a giggle as she averted her gaze from Twilight’s.
“That particular word did have a rather different connotation at the time, yes. It is rather subtle however. I’m impressed that you were able to pick up on it.”
“I’m amazed that I’m the first pony who’s picked up on it in a thousand years,” said Twilight, raising an eyebrow.
“I imagine you’re not,” answered Celestia, smirking a bit, “just the first who was cheeky enough to point it out.”
Twilight’s face slowly split into a wide grin. Using her magic, she grabbed a fresh scroll and a quill from her desk and hopped up onto her hooves. Then she trotted over to Celestia, still grinning as she took up a position behind the alicorn. Celestia’s blush grew darker as she craned her neck around to look at Twilight.
“What are you doing back there?”
“Writing poetry!” said Twilight. Celestia telekinetically attacked her with a pillow.