The light from Celestia's noontime sun brightly shone into Twilight's sleeping face, causing the unicorn to cover her face with a foreleg. "Mmmph, 5 more minutes... I was up studying, ma..." Twilight's voice, still drowsy, didn't want to give in to the warm sun ray's urging her awake.
But, try as she might, the warmth from the sun gently urged her from her slumber. Giving a sigh, the unicorn slowly opens her first her left eye... Then her right eye creeps open as she stumbles out of her sleeping nook. Still half-asleep, Twilight trips down the steps and into the kitchen. "Mmmm, need tea... Wha-what happened last night...?" The last thing she remembered as she trotted drowzily into the kitchen, was being at the local Mare-day Gras party Pinkie Pie threw last night...
"Twilight!" The ever-hyper pink pony bounced over, her neck laden with what looked to be hundreds of beaded necklaces as she wore a mask in the shape of two lollypops over her eyes. "TWILIGHT!" the hyper pony screamed again. "Ya' gotta try this sweet party drink Honeypot brought! It's a new drink she made called 'mead'! It's super sweet!"
"Okay, Pinkie, I'll try a glass..."
Twilight's brain was still in a haze, trying to swim through the fog of memories as a splitting headache started to creep across her head. "Oooh..." Twilight groaned out, resting a hoof to her brow as she steadied herself against the counter. "I feel like there's a parade in my head, and my body feels like I just ran the Running of the Leaves five times in a row..."
"Woo! Look at me!" Twilight danced on a table around her 17th mug of the sweet drink, a griffon mask over the top half of her face as she shook her rump in the air with abandon. Several of the more 'promiscous' stallions (And a few mares) watched closer than decorum dictated.
Pinkie reached up, trying to tug on Twilight rear hind leg. "TWI-I-I-ILIGHT! You're drunk! You need to get off the table and go home!"
"Don't bug me, Pinkie! It's Mare-Day's Gras! I finally understand why people get drunk! Woo-hoo! I'm queen of the world!"
Twilight shook her head again. The memories of last night, hazy as they were, were starting to come back to her. "I... I wasn't... Drunk last night, was I?" Using her magic, she set a kettle of water boiling on the stove as she turned to look out into the main library casually. "Now, where did I put... My... Tea!?"
Twilight ducked behind the counter, the pony now wide awake as her heart beat rapidly in her chest. She shook her head rapidly, trying to make herself believe what she saw was just a hallucination. "Now Twilight..." she mumbled to herself still in shock. "You're going to turn back around, peek over the counter, and everything will be normal! You're still feeling the alcohol from last night, so you're just seeing things..."
Two purple hooves slip up over the counter, and slowly Twilight's horn begins to creep up into the air from behind the counter. She raised her head high enough to peek back into the library... Then suddenly ducked her head back behind the counter with an 'Eeep' noise. She hadn't imagined it. Standing in the middle of the Library was Princess Luna... Wrapped in HER blanket!
Twilight's body splayed out against the counter's back, her chest rising and falling in a hyper-ventilation as she heard a soft voice call out, "Twilight, hon... Come back to bed... It's too early for us to wake up! Especially after last night!" A small, shy giggle filled the air as Twilight swallowed hard. Suddenly, the events of last night started to come back to her in full...
The mayor of the town looked between the two ponies and studdered. "B-b-but Princess Luna! Are you sure you and Twilight Sparkle want to do this right now? Perhaps you should wait until morning, after the alcohol wears-"
The drunk princess raises a hoof in anger. "Nuuuuuuuuuuuu! Celestia has the day! The night is... Um... Yeah! Mine! And so is Twilight Sparkle!" She leans against Twilight as her eyes flutter closed. "Mmm, mine for*hic*ever an' ever..."
Twilight nuzzled into the drunk princess's neck as she nodded in agreement. "Yah... I'ma the queeeeeeeeeeeeeeeeeeeeeeeeeeeeen.... Of the world... An'... *hic* An' Luna izzzzzz.... Iz a'my princess... Now finish it!"
The mayor shook her head sadly. "Well, Celestia help me, but as the mayor of the town I now declare you Mare and Mare... You brides may now kiss..."
The two night ponies turned, slowly opening their eyes, before leaning in for a drunken kiss before the town.
"There you are, hon!" Luna's head peeked around the counter as she smiled softly. "You've made me so very happy, Princess Twilight..."
Twilight did a double-take and swallowed. "P-p-p-princess!?"
Luna nodded softly. "Well, of course! You married into royalty! That makes you a Princess now!"
Twilight raised her forehooves to her brow. "Oh no, Celestia is going to kill me! I'm never going to drink ever again!"
Luna laughed softly and nuzzled into Twilight's mane. "Well, she can't kill you, or she won't be able to be an aunt! Or did you forget that spell we did during our Honeymoon night?"
The final memories break through the foggy haze as poor Twilight slumped down further against the counter. "You don't mean...?"
Luna just smiled again and nosed her new wife. "Well, you do have the larger body. It's more fitting for you to be the mom. Now come back to bed, love..."
Realizing that she was now with foal, Twilight did the only thing a pony in her condition could do at finding out she had drunkenly married the Princess of the Moon - and been knocked up in the same night... She fainted. As blissful unconsciousness filled her head, one nagging thought crossed her brain.
"Does this mean Princess Celestia is now my sister?"
Somewhere in Canterlot, the entire palace shuddered with Princess Celestia shouting out "WHAT?!?!" as birds flew away in fear en-masse. But that' another story for another day...