Celestia was sulking.  The entire castle staff was terrified and three-quarters of the way to outright panic.  The only thing keeping them from stampeding straight out the door and over the side of a balcony was the fact that Luna had given them the most amazing sigh and roll of her eyes when they had informed her that her sister refused to open her chamber doors.

It was hardly worth getting worked up about, as far as Luna was concerned.  Celestia was still moving the sun on schedule, wasn't she?  Yes, she certainly was—and that meant it was a minor tantrum on the lifetime Celestia scale.  

Why, a day barricaded in her bedroom was nothing, it was a long, long way from measuring up to the best pout that Luna could remember.  That time, Celestia had stayed in her room until everypony that could possibly have seen and remembered what happened had died of old age—and there had been an infant at court that day, so she had ended up waiting eighty-seven years.  Eighty-seven years of ruling by notes slipped under the doorjamb!  Granted, that had been nearly two thousand years ago and they had both been much younger mares then, and also granted, Luna had not read of any notable reclusions taking place during her absence, but...  Well.  Certainly everypony was panicking prematurely, as usual.

Nevertheless, they already wore on her nerves.  No matter how dismissive she acted—even when she changed tacks completely and attempted gentle reassurance!--the castle staff continued to hover at the edge of anarchy.  They came to her every five minutes to tell her again and again about how her sister still had not emerged; a different pony every time, but each one sharing the disheveled mane and pinprick, nervously-shifting eyes that were swiftly becoming a palace uniform.

Luna would have to put a stop to it, if only for her own sanity's sake.  The moon was nearly full; it was as fine a time as any to confront the daymare in her lair.

***

Luna Revenio, Crown Princess of Equestria, Mistress of the Moon and Stars and Repeatedly Irritated Sister coalesced as quietly as she could from the glittering, dark cloud that had seeped through Celestia's door.  The silk-on-silk sound of her passage was not quiet enough, however—before she could take her first step, a goblet clattered to the floor, bent askew by its impact with the wall three feet above Luna's head.  The moon princess shook her head silently at her sister's sloppiness, then paced slowly up behind her.

Celestia refused to acknowledge her sister past the welcoming missile.  Instead, she glared out the window at her sister's moon and did her best to radiate a simple message: Go away!  I'm ignoring you!.

Luna, in turn, did her best to ignore Celestia's ignoring.  As the larger alicorn swigged from her glass, Luna snagged the bottle her sister had been steadily emptying into it in the glow of her magic and pulled it over to her nose.  The whiff of strong, distilled spirits and apples--mostly, at least--sent her eyebrows crawling up toward her mane.

“Apple-jack?”

For the briefest of moments, panic washed across Celestia's face.  Then she realized which applejack her sister meant, and did her best to return to aloof perfection.  She was pretty good at that, admittedly.

“Yes,” she declined to elaborate.

A thousand years away or no, Luna could still read her sister like a book, especially when she was sulking.  The momentary distress did not go unnoted, unconsided, or uncatalogued--it was all absolutely classic.

With exaggerated casualness, Luna poured herself a glass of the apple brandy.  With equal nonchalance, she appropriated the chaise next to her sister and removed the champron she had borrowed from the royal armory.  Finally, with a deliberate air of unconcern, she began her probe.

“So, sister.  What did we miss at the wedding?”

Luna watched a crack spread across her sister's glass, “You know what happened, sister.”

Luna put a bit of cheer into her voice as she continued, “Oh, not precisely.  We gather that thou were beaten, certainly.  Hurt.  Imprisoned... in an apparently quite repulsive construction of unthinkable changeling secretions.”

Celestia's jaw clenched visibly, but she remained silent.  Luna, for her part, glanced up at the ceiling, as if taking a purely academic interest, before concluding, “...all in front of thy faithful student and the other Elements, of course.”

The glass crunched abruptly into a compact sphere of sparkling dust and amber liquor.

“We are sorry we missed it, sister.  Truly,” the telekinetic grip on the remains of her drink began to relax, but too soon, “...we would have liked to see the perfect princess out of control.”

That was enough.

The larger princess was silent for a moment, then lunged abruptly for her sister, flinging the remains of her drink aside.

***

Almost immediately, the alicorns burst through the window and onto Celestia's balcony, sending shards of glass tumbling, glittering, into the night air.  Celestia was the first to begin pulling manes, and it was in trying to dislodge her sister's grasping teeth that Luna accidentally pushed her sister over the railing.  Unsuccessful at the attempt to untangle herself from Celestia, Luna was immediately pulled by her hair from the top of Canterlot and into thin air.

***

They landed side-by-side on the steep slope of Canterlot mountain with a teeth-rattling thud, but celestial goddesses are made of tough stuff; it wasn't even enough to force a pause in the fight.  Somewhere in mid-air, Luna had hooked a slipper in her sister's golden peytral, and now neither piece was anywhere to be seen.  No matter.  Celestia rolled on top of Luna and wound a hoof back to slap mercilessly at her foe.  She didn't get the chance—Luna used the slope to unbalance the larger alicorn and send her rolling downhill and onto her back.

“Ha-HAAAAaaaaa--,” Luna's cry of triumph trailed out into a cry of surprise at the shortness of her victory--Celestia promptly pushed off with a wing to keep the downhill roll going until she was back on top.  Luna repaid her in kind, then stuck out a hoof to stop the roll with herself on top, this time.  This is when they both discovered their mistake.

Luna's hoof simply bounced them up a bit, and they kept rolling anyway, faster and faster down the mountainside, both voices joining in a ululating chorus.

“WaaaAAAAAAaaaaAAAAaaaaAAAAAaaAAAAAaaaaaAAAAaaaaAAAAAAAaaaaaaaaa...”

Everything was a rapidly spinning blur, and it all came to an abrupt stop with an immensely loud, hollow THUNK and a gentle shower of leaves.

Neither one of them laughed first; it was a mutual decision, a moment of shared sisterly intuition.  It started out with gentle chuckles, then they both imagined themselves as a blue and white blur spinning down the mountainside, and it became shared guffaws.  Finally, Luna glanced up and broke down completely, falling onto her back and pointing a hysterically shaking hoof at the sign hanging from the tree they had just rolled into.  Twilight's library!  Oh heavens!  Tears streamed down both alicorns' faces, and they leaned on each other for support in their hilarity.

Eventually, the laughter slowed, and Celestia carefully wiped the corners of her eyes with the back of one hoof.

“Luna, really though... you have no idea how disgusting that cocoon was.”

They both dissolved into a new fit of giggles.

***

Twilight awoke, and immediately wished she hadn't.  The last thing she remembered was falling to her knees as the entire library shook to an immense impact, and now the only thing she could feel was the sharp pain of an enormous goose-egg on the back of her skull.  Opening her eyes, she found herself  facing the copy of The Shorter Ox-ford Equestrian Dictionary (A-L) from the top shelf, and drew the obvious conclusion: she had blacked out trying to memorize the dictionary, again, and had repressed the memory of the experience, also again.

She groaned and attempted to struggle to her hooves, then squawked like a surprised waterfowl when she found herself enveloped in an unfamiliar magical field and gingerly lifted onto her hooves.  It didn't take her long to find the source of the telekinesis, as that source began speaking to her immediately.

"TWIL--Twilight!  We are relieved to see that thou art unharmed!"

Twilight forced her eyes into focus, and her expression drifted into one of confusion.  Luna and Celestia were both there, at the library table with the ridiculous stylized equine bust that Rarity kept trying to break, burn, or steal, with a barrel upended between them.  Both princesses were wildly unkempt, their manes and tails divided into numerous streams that curled and crossed one another and which each seemed to wave with a different invisible wind.  There was dirt rubbed all over both their coats--though it was a bit hard to tell on Luna--and even a few angry-looking scratches showing through the fur.  They were both smiling, though--grinning, even!--and even in her daze, something in Twilight latched hungrily onto the contentment radiating from Celestia's features.  That was not enough to keep the question from tumbling out of her mouth, though:

“Have you two been... fighting?”

“No!”

“No, no!”

“Certainly not!”

“Unimaginable.”

The alicorns looked at each other.

“I... fell,” ventured Celestia.

“Yes!  She fell, and then, ah, we fell trying to help her up.”

“Oh yes!  We both fell.”

“Yes.”

“Certainly.”

There was a long pause.  Twilight looked from one alicorn to the next, and both princesses held their best beatific expressions, both doing an admirable job, all things considered, of not glancing nervously at her sister.  

Luna began to wilt under Twilight's stare, and rose abruptly.  She began to approach with a loose, affable gait that seemed to Twilight to be utterly alien for one of the princesses to be using.  As she watched Luna come closer, she couldn't help but connect that gait, the princesses' disheveled appearances, and the fact that they were both completely without their royal regalias, and come up with a blush that she did her best to hide.

Luna's brows knitted momentarily, and Twilight felt a familiar magical shift which told her that Luna was now using her telekinesis to give Twilight a once over--all over.  Nothing that Twilight hadn't endured a dozen times before at the horns of her doctors, but here--she dipped her head as she blushed a little more deeply.

"Moon's Maria, Twilight!  Thou hast taken a terrible blow to thy noggin!  We had thought thou had merely attempted to memorize the dictionary again."  Luna's tone shifted from declamatory to something gentler, edged in concern, as she continued, "Allow us, please..."

Twilight nodded, and then her whole body sagged in relief from the soothing waves of Luna's healing magic lapping out from the lump on the back of her head.

"Ohhhh, wow... yeah.  Thank you, Luna."

A warm smile had returned to Luna's face as she replied, "Always, for--" there was a pause, and her smile turned gently wry, "--my friend."

Twilight smiled at the shared joke, and both she and Luna missed the expression that passed across Celestia's face as she watched the two ponies most precious to her so easily resume such an easy familiarity.

***

Celestia hid her mouth behind the coffee mug full of her student's carefully hoarded cider.  She had downed about twelve mugs full so far (being so large made her a very expensive date), and at this point it was enough effort merely to school her eyes to their familiar maternal warmth.  Twilight and Luna's conversation had gradually drifted away from her, and she found herself reflecting darkly on how natural it felt to watch, silently benevolent and aloof, as other ponies made friends and enjoyed themselves.  A corner of her mind also noted clinically how using the cider as a prop left her drinking more and more of it to keep up the facade.

She hadn't realized she had zoned out completely until she was snapped back into awareness by the sound of Luna giggling--shyly?  That wasn't a sound Celestia had heard since... well.  Far in the back of her head, the same clinical voice began to pontificate on how good it would be for Luna and Twilight to get together--for both of those precious ponies--but by the time it bubbled up to Celestia's forebrain through the cider, all she could hear was 'glub blub gurgle blub'.  She stood up suddenly and swayed on her hooves.

The white alicorn's sudden movement silenced both other ponies, and they both stared at the sun princess with wide, slightly guilty eyes.  Celestia paid their reactions no heed, though, and strode across the room to them with truly laudable steadiness.  She hauled all six limbs to a stop, looming above the pair and staring down at them for one long moment.  Twilight and Luna shared a brief glance before fixing their gazes back on Celestia.  Twilight attempted a smile for her mentor, but it came out small and flighty, and melted as Celestia fixed her with the full radiance of her regard.

Before Twilight could gather the courage to ask Celestia what was wrong, the sun princess struck.  Celestia dropped to her knees, and her wings snapped forward, the long primaries meeting behind Twilight's flank and brushing it in passing.  Twilight startled forward instinctively from the unexpected contact, and that put her right where Celestia wanted her to be.  Before the unicorn mare could make another move, Celestia dipped her head and pressed her lips to Twilight's with a burning intensity.

Twilight squeaked at the back of her throat--her eyes were wide and her pupils shrunken, but part of her yielded immediately and eagerly to the press of Celestia's tongue at her lips.  It was a demanding, fiery warmth in her mouth, and it was the easiest thing in the world to shut down her mind and give it over to the lust she thought she had corralled, tamed, and broken years ago.

All too soon, Celestia broke the kiss, pulling a noise of protest out of Twilight as she leaned back.  She turned her head and regarded her sister with half-lidded eyes.  Luna's mouth still hung open in shock, her eyes wide, her brows knit, and her ears folded back in naked betrayal.  There was a suspicious moistness in those eyes, and Celestia could see the gears turning in Luna's head as the dark goddess began to gather her hurt into a cloak of anger.

Celestia couldn't stand it.  She couldn't let her sister be consumed by such emotions again, so she did the only thing that came to her cider-addled mind: she leaned over and kissed Luna too.  Her eyes were screwed up tight, like a pegasus foal throwing herself off a ledge for her first flight, but she lavished Luna with the same intensity and passion she had heaped upon Twilight.  When she broke this kiss, Luna was staring at her in a very different kind of shock, taking quick, shallow breaths.

"Tia--!  We haven't--!"  Luna cut off her own harsh, loud whisper before trying again, "But--not since we created ponykind--!"

Celestia interrupted before Luna could find any more protests. The white alicorn was actually smirking, full and lopsided and brazen as could be, “Don't you like me out of control?”

The smaller princess was silent for a moment, then lunged forward and embraced her sister.

***

Twilight awoke, and immediately wished she hadn't.  The last thing she remembered was... was... was clearly and definitely a dream that would no doubt spring back to mind and turn her beet-red at the worst possible times for the rest of her life, oh Celestia.  Augh, no!  Swearing by Celestia was definitely not in order here, oh---something.  She'd think up something later.  Twilight groaned and draped a foreleg across her eyes, then rolled onto her side.  That's about when she woke up the rest of the way, despite her hangover, because she found her nose pressed into the soft, dark fur of Luna's back.  Twilight stared at the dark expanse, but Luna continued to snore daintily, curled up in a tight ball with a wing over her face.  She found herself remembering her--surely it had been a dream?  She could remember so clearly, though, how surprised she had been by Luna's soft coat, and how it had felt pressed up against--

Oh wow.  Twilight was certain she had never blushed like this in her life, not even when Celestia had caught her with the copy of the Pony Sutra, and she'd thought she was going to blush right to death then.  Celestia had just smiled at her, though, and Twilight had gabbled something about research on pre-classical equine civilization, and, and...

Twilight rolled suddenly to her other side as more pieces of the night fell into place, but there was nopony there, and she felt a strange mix of profound relief and profound disappointment at that fact.  She caught a fading whisper of the familiar scent of her mentor's favorite soap, but that was all.  She stared out the window at the early-morning sky for a long moment before carefully shuffling out of bed and quietly making her way down the stairs.  She was making a direct, focused line for the kitchen, but a strangled, GURK sort of noise stopped her in her tracks.

It was Spike.  Sitting in his basket with his knees clutched to his chest, leaning back with the support of his tail flat to the floor behind him.  He stared back at Twilight with bloodshot, baggy eyes and pinprick pupils, breathing slowly and deliberately.  Suddenly, he stood up.

"I'll be at Rarity's."

Twilight could only nod.