The Royal Court of Twilight. Specifically, the Two Courts of Dawn and Dusk.
It is considered the most important court in all of Equestria, for it is the time when both Luna and Celestia are (fully) awake to see through the nation's most important matters.
The time was evening, the weather now heavily snowing and a grouchy-looking Luna sat upon the Royal Throne. The Guards, Spoken Softly, the prosecutors and the audience within the Court stared at her glowing red nose.
It actually illuminated, casting a light red shade on Spoken's face.
He also made sure to wipe her snot the second it dripped.
"Spoken Softly?" said Luna.
"Y-y-y-es, Your Majesty?"
"Where is the Princess of the Sun, whom I would rather not meet right now but is due for Court?"
"I'm not sure Your Majesty..."
"Then I shall proceed without her,"
"B-b-but, The Twilight Court is supposed-"
"If she cannot make time for Court, then I shall have to pick up her slack. Now get me the podium," said Luna bitterly, then muttered under her breath, "...sooner I get this over with, the faster I can escape from that mare..."
Spoken promptly flew away and came back with a large podium, complete with the related documents, a sounding block and an insignia in front that was of the Royal Equestrian Crest. He placed it deftly before the Royal Throne.
Typically the block would have a gavel involved; but recently, it was either Luna using her bare hoof to do it, or Celestia asking Luna to knock it, as she liked to knock it.
And Luna did knock the block, thundering the palace and trembling the earth. It brought a satisfactory nod to Luna's stony expression, "BRINGETH IN THE PROSECUTED,"
And the Throne Room's giant doors opened to reveal the escorting guards and the prosecuted: the infamous Flim Flam Brothers.
They were brought before Luna, and they too stared quizzically.
And Luna brought her hoof down on the sounding block again. "COURT, IS NOW IN- HAAA-"
And with a reaction that has been clearly practiced and repeated, Luna bolted off as a literal lightning bolt, right out of a deliberately, slightly opened window.
"-CHOOOO!! ...errghh-bur-bur-burgh..." and she flew back in groggily with a bit of airborne assistance from Spoken. Some snow was on her.
Luna settled back down, Spoken wiped her nose clean and the snow off again, and without missing a beat, "-SESSION!!"
And she looked down at them; Flim and Flam smugly stared at her. "What, pray tell, are you two looking at?"
"Well-well-well, Your Nightliness," began Flim, "That's quite the schnoz you have there!"
"Weather has been gettin' you down, eh!?"
"Not a problem, Princess, we can brew a most magnificent concoction that will-"
Luna magically grasped them by their necks, and pulled them all the way to her face.
"Thou willst only speaketh with our expressed permission...!" hissed a very, very short-tempered Luna, her bright red snout forcing the perspiration out of the brothers, "Do we make ourselves *SNIFF* clear...!?"
The dangling, struggling stallions nodded in fear, and lack of air. She then placed them back before their escorting guards, and released the choke so they could gasp back their breath.
Spoken slid the relevent document to Luna, to which she haughtily bellowed to the Court, "Flim and Flam! You have been brought before the Court of Twilight, before the Royal Pony Sisters, myself, Princess Luna, and Princess Celestia, who for I am very sure is absent for very important reasons, but, is nevertheless, here with us in spirit to carry out the sentencing of Flim and-"
"YOO-HOO! SISTER!!" happily echoed a pure and melodic voice.
"Flaaaaaaaaaam..."
And the giant doors opened to reveal the Sun Princess herself, looking to be in a good mood and most crucially, Page Turner sheepishly levitated a large sack behind her.
Her happy trots echoed in the room as everyone stared at her sack that read CELESTIA'S BABYSITTING BABY SISTER KIT.
"Hi boys," she chimed at the Brothers as she passed them by.
"Hiii Princess Tiaaaa...!" swooned Flim and Flam as she passed them by, sighing deeply.
And Celestia finally sat exactly right beside Luna, a little too snugly to her in fact. "Little sister, sit up straight," said Celestia matronly, "You look silly, looking all red-faced and gloomy down there!"
Luna's snout was almost parallel to the podium's surface, her face and horn sticking out. The crowd could practically feel her frustration emanating, but her elder sister remained serene.
"Celestia... why did you greet the prosecuted...?" hissed Luna in a quiet rage.
"It is important to be on friendly terms with everypony in this day and age, sister!" whispered Celestia, obviously whispering merely to humor her beloved sibling.
"But they are being tried for their crimes, sister...!"
"And they shall be put to trial justly and firmly, I assure you,"
"Fine...! Now the least you could do is apologize to the Court for being late...!"
"Alright, alright," said Celestia, who then turned to the Court, "My faithful subjects, I must apologize for my late presence, I assure you, it will not happen again!"
Luna closed her eyes and sighed, and began to straighten her back and-
"For you see, I had to bring in extra equipment to take care of my stubborn little sister!" she proudly announced, proudly lifting the sack high in the air.
Now the Court could only see Luna's horn sticking out of the podium.
And the Big Sister continued, "Now I am sure you are wondering, equipment? For a mere little cold? Well, as some of you may very well know, my sister never plays it as a lightweight, doesn't she?" she said with a wink.
The Court giggled. And Luna's face, underneath the podium, was now as red as her nose.
"Oh no-no-no!" Celestia continued even more enthusiasically, "My sister has always done things as a heavy-duty! Have a tantrum? Thunderstorm! Lost her favorite action figure? Nation wide witch-hunt! Have a sneeze? Hurricane! That time of the-"
"SISTER!!"
"Oh, right, nearly said something inappropriate there! To put in short, since my sister is so stubborn in not taking proper care of herself, I shall be assisting her in sentencing the Flim-Flam Brothers and tending to her illness consecutively, as a good sister should,"
Some of the members of the Court actually 'aww-ed'.
"Now, as you were saying sister? Before I came in?" she said to Luna.
Luna remained underneath. And truthfully, she'd rather wish the podium would just swallow her up and never spit her out.
"Sister, no slouching!" said Celestia as she spanked her up the rear, which caused Luna to yelp and bolt straight up.
"Ahem, right," said Luna, attempting to control her composure, "Let us get on with this. FLIM AND FLAM! You have been brought to court for multiple crimes of..."
And she read the list, "Extortion! Gerrymandering! Various forms of fraud! Impersonating as two sisters in a Sisterhooves Social- wait, what?"
"Aww!" said Celestia as she leaned over to look at the evidence of the last crime, "They have photographic evidence of Flim and Flam dressed as fillies! You two looked lovely in these sundresses!"
Now it was the Brothers' turns to be red in the face.
"I told you that was a stupid idea!" Flam snapped at Flim, "But would you listen, brother!?"
"We needed that prize money, brother!" Flam snapped, "It's not as if you were thinking up of any ideas!"
"I had to shave off my beautiful mustache for that gig! It was weeks before it grew back!"
"By Celestia's mane, stop reminding me! We live in the same cell, have meals together, sleep in the same room, OF COURSE I KNOW IT WOULD TAKE YOU WEEKS TO GROW-"
And that was Luna's cue to knock the sounding block, where the sonic resonance slash reverence finalized the argument.
"No talking from the prosecuted," ordered Luna, who then glared at Celestia, "Or from other bodies for that matter..."
"Oh, I have no idea what you are speaking about sister," chimed Celestia sweetly.
"Now then, Celestia and I shall now briefly review the various offences," announced Luna to the court, "From which we shall gather our proper opinions whether as to allow The Flim Flam Brothers an appeal or to sentence them, here and now,"
Spoken Softly and Page Turner passed Luna and Celestia the criminal files of Flim and Flam, respectively.
Luna began to intensively scan Flim's very extensive criminal records, cross-examining evidences, searching for contradictions and any procedures that might have gotten out of hand.
Just as she was about done looking at Flim's first criminal case, she felt a familiar soft material wrap her body.
"Celestia," whispered Luna intensely to a Celestia that looked as if she was focusing on Flam's case file, but a mischievous smile was present, "Kindly remove your stupid old blanket off of me,"
"You are cold, little sister," said Celestia, without taking her eyes off of her case file.
"I am not cold sister,"
"Don't argue, your big sister knows best," chided Celestia softly, and began to magically wrap Luna up into the Lunar-rito again.
"Sister! You will do no-"She began to rebelliously fight back, grunting and struggling, but Luna realized the entire Court was staring at her.
Luna blushed hard; she has made a fool of herself enough times already, and resided her fate as a Lunar-rito. At least Celestia had the courtesy to magically tilt Luna at the right angle to read the files.
"Ah, Luna, there is a case here from Flam I want to cross-examine with Flim's file," said Celestia.
"Of course sister, just let me- urrghhh!" Luna tried to wiggle her fore-hooves out to reach the file, to no avail.
Celestia giggled at the sight, and then snuggled her horrified sister, "Oh Luna! No need to exert yourself! I'll just take that from you!"
Again, members of the Court went "Aww...!" at the sibling love, the one-sided sibling love.
And Celestia slid her Flim's file to herself and began to read, and flip the pages, read, and mark, all whilst Luna stared at her.
"I know what you are doing, Celestia," muttered Luna.
"What do you mean, Sister?" said Celestia softly as she flipped both pages of each file.
"You're going to hog all the work from me, so that I will have no choice but to be mothered by you!" yelled Luna.
"Now, sister, no shouting, it's not good for your throat," Celestia said firmly, but Luna frowned and magically swiped the two files away, "Hey! Luna! Give those back!"
"No! I need to work!" yelled Luna again, whose magical aura took over the Lunar-rito and she turned away in a huff, scanning the files again.
"Luna... give those back..." ordered Celestia with her Big Sister Voice. She gasped when Luna's ears went flat to close out the her voice.
Peace at last, thought Luna, finally getting the momentum she needed, and then suddenly, her files poofed away and a squarish, pastel-colored thing shoved in her mouth.
She felt a familiar liquid going down the throat, and she spat the magically floating object out. She contorted and squirmed, and slapped the taste out of her mouth.
"Aarghh!" roared Luna, "CELESTIA!! What was that!?" she finally saw what the squarish thing was, "A baby bottle!? You put your soup that is as old as me into a baby's bottle!!?"
"It's not a baby bottle, sister, I won't go that low," explained Celestia, "It's a new invention, called a sippy cup,"
"It looks like a sports tumbler meant for a filly!" retorted Luna.
"That, Luna," and Celestia smugly smirked to Luna, "is the idea,"
"Why you arrogant, confounded, oversized- MMH!" and the sippy cup was shoved in her mouth again, and stayed there.
"Now now sister, let the ones fit to work continue with the work, you just stay there and rest," she said sweetly again, giving her a little kiss on the cheek, floated her off to the side of the podium, and proceeded to read the files again.
This created a really big "Aww...!!" from the Court. Luna's face went red again, and sunk her head deeper into the Lunar-rito, and the sippy cup, now magically stuck to her lips, was dragged down into its crevice as well.
"Alright everypony, I have finally made my decision concerning Flim and Flam," announced Celestia to the Court.
Spoken Softly looked at her Princess, clearly upset that she was bested, why, it almost seemed as if she was heaving inside. Spoken realized she wasn't heaving due to sadness.
"Oh dear! Princess Luna!" exclaimed Spoken, who yanked the Lunar-rito slightly down, to reveal that Luna was once again trying to hold back a Royal Canterlot Sneeze.
But this time with the degree of wriggling, and squirming that she was doing, and how strained her face was, this was the mother-load.
"Princess Celestia!" shouted Spoken softly to Celestia, "Princess Luna's about to blow!"
Celestia's face spun and stared in horror at him, her jaw dropped at what Spoken, of all ponies, just said. Then she stared at a struggling Luna, and then said, "Ohhh!'
"W-w-we must take her outside right now, Princess Celestia!" Spoken exclaimed again, "O-o-or she'll be so upset when she sneezes at everypony!"
The Court gasped and took cover, either by ducking or hiding behind somepony else. There have been a few accidents already when a few ponies got caught in the crossfire of The Royal Canterlot Sneeze, and the collateral damage was not to be trifled with.
Celestia giggled again, "Not to worry, my former assistant, I have the tool for just this situation!"
And she pulled out from the CELESTIA'S BABYSITTING BABY SISTER KIT, a large, sparkling blue handkerchief, adorned with the Lunar Crest.
"This specially made hankie is weaved from pure Diamond Thread!"explained Celestia, "Nothing but a dragon's bite can chew through this material!"
And Celestia magically yanked the sippy cup out, which Luna heaved back as far as possibly could, and Celestia steadied the Handkerchief to catch the Sneeze.
"HAAAAAAA-"
And her snout impacted directly on the Handkerchief.
"CHOOF!!"
It was an extremely muffled sneeze and nothing came past the handkerchief; it had done its job well.
Too well in fact, for the snot and released pressure from the Sneeze backfired on Luna.
In an instant, her entire head and the Lunar-rito and even part of the Royal Throne was covered with her transparent snot.
Celestia, Spoken, Page Turner and the Court stared in horror.
"Oh sister! I'm so sorry!" Celestia cried, and finally dropped the vice-grip of her blanket and it fell, revealing Luna's body.
Luna could feel the snot covering her face. She touched it with one hoof and could feel its drippy stickiness.
Everypony stared at her, jaws agape.
And for the first time in a long time, she began to cry.
First softly, and then loudly, and then LOUDLY.
Luna felt so ashamed as she wiped the snot forcefully from her face, sniffling and sobbing her eyes out, her tears mixed with the snot.
"Oh sister, please don't cry! Please don't!" pleaded Celestia, as she attempted to assist Luna, but Luna angrily swatted her lanky hoof away.
"DO NOT TOUCH ME ACCURSED SISTER!!" yelled Luna, still sobbing, "I HAVE HAD IT WITH YOU!! I AM DONE WITH YOU!! YOU HAVE SHAMED ME BEFORE OUR SUBJECTS FOR THE LAST TIME!!"
The weather outdoors began to blizzard harder than thought possible. Lightning struck, and the winds howled.
"Sister, I didn't mean for the hankie to backfire on you!" reasoned Celestia, "Let's get you out of here where-"
"I SAID TO NOT TOUCH ME! I MERELY WANTED TO BE LEFT IN PEACE WITH MY WORK BUT YOU JUST HAD TO BE THE BIG SISTER, THE GUARDIAN, THE ETERNALLY PERFECT CARETAKER OF THE PATHETIC, USELESS NIGHT PRINCESS WHO IS UNABLE TO DO ANYTHING FOR HERSELF!!"
Celestia herself was tearing up, "Luna, Luna p-p-please, don't be-"
"THIS IS THE FINAL NAIL IN THE COFFIN, CELESTIA!!" yelled Luna grimly, "I NEVER WANT TO SEE YOU AGAIN!!"
And with a final, piercing, hurt glare, the snot-covered and sobbing Luna teleported away. And the blizzard howled an icy scream.
Celestia held her head low, tears flowing freely down. Spoken Softly jitterly went up to the podium and attempted to announce, "T-t-t-he Twi-twi-twi-"
Page Tuner helped, "What my associate is trying to say, is that Twilight Court shall resume at a later time and today's Court shall be postponed,"
And the members of the Court all left. And as Flim and Flam were escorted out, Flim whispered to Flam.
"Well, that's as interesting a trial as it can get, eh, brother?" commented Flim quite neutrally.
Flam said nothing.
"... you're still mad at me about the moustache, aren't you?"
Flam replied by looking away with a huff.
"Oh come on! Just because Princess Luna can huff away, that does not mean-"
And the Throne Room doors were closed, leaving only Spoken, Page and Celestia, still silently weeping.
"Princess Celestia?" said Page with concern, "I think we should go,"
But she was in deep thought, Celestia. For she cannot get that image of Luna glaring at her with such hatred at her out of her head, or the words, 'this is the final nail in the coffin, Celestia. I never want to see you again,'
That was the second time that Luna had said that to her.
The first time was when they argued for the nth time on Luna's increasingly antisocial attitude.
After that argument, Luna was transformed into Nightmare Moon.