"I don't think this is a good idea."
"What about this is a bad idea?"
"Oh, I dunno, aside from the fact that you're planning on stealing from a princess!"
"C'mon, you're still stuck on that, Twilight? I already told you, this is gonna be in and out, no fuss. She won't even realize it's gone."
"Rainbow, we're friends, but if we get caught here I'm going to tell the guards that you forced me to come here against my will," Twilight said, her head snapping from left to right as she danced on her hooves.
Rainbow Dash forced open a window, tossing away the crowbar before pulling a ski mask over her face. "You do know you can walk away at any time, Twi, right? You've already done your part with the spell and the saddlebag."
Twilight shook her head, her eyes narrowing. "I'm here to make sure you don't get sent to the moon, or turned to stone, or locked away in Tartarus, or sent to the moon while turned to stone in Tartarus! Besides, I have plausible deniability."
Rainbow Dash fastened her saddlebags around her waist, peering down through the window. "What, are you gonna say you were just up on the roof of Canterlot Castle for a midnight stroll?"
"I'll tell them I took a few wrong turns!"
Rainbow Dash rolled her eyes. "Uh huh, we'll see how that works out for you, egghead." As Twilight simmered, Rainbow put a leg over, hanging halfway through the portal. "Alright, I'm gonna fly in, grab the thing, and fly out. It should be five minutes, tops." Twilight gave her a look of worry. "And don't look so glum, Twilight! Remember, we're helping out Celestia here, even if she doesn't know it."
Twilights ears perked at that, and she nodded as a look of determination overcame that of fear. "You're right, Rainbow. I wouldn't be her number one pupil if I didn't do anything!" She approached Rainbow, her horn lighting up. "I've revitalized the hoof-silencing spell; it should hold until you're finished with this mission of yours, but remember that you have no more than ten minutes before it expires. And for Celestia's sake, stay out of sight. Just because the guards won't be able to hear you doesn't mean they can't see you." Twilight's eyes shifted to the pegasus' prismatic hair. "You're rather... noteworthy."
"Psh, calm down," Rainbow responded. "I read about this type of stuff all the time in my Daring Do comics."
"Do you think those have any basis in reality?"
"Twilight, I crash into things almost daily and still have reasonable health insurance, you're the pupil of a millennia old sun deity and you put down everything that threatens Equestria with a beam of friendship, and Pinkie Pie is Pinkie Pie. Do I seem very unreasonable given the circumstances?"
Twilight blinked. "...Point taken."
"Thank you, now if'n you don't mind," she said, rubbing her hooves together with a mischievous grin, "I've got a MacGuffin to misplace!" With that, Rainbow allowed herself to fall into the castle proper.
She opened her wings to slow her descent, drifting silently through the air above the throne room. Princess Luna was on the throne, looking bored half to death as somepony well into middle-age―who dressed as though she were twenty years younger and had a haircut that was synonymous with menopause―droned on and on about how little recognition she was getting at the local Mid-Life Crisis Club as the mother of two adopted gryphons and the wife of a wealthy politician who was a few days away from kicking the bucket. She went on to talk about how tolerant and pure of heart she was before inevitably shifting the focus of the conversation to her vanity, insanity and lack of humanity (in terms of her ability to empathize and feel compassion for other living beings, and because the audience reading this is most likely of the homo sapiens species).
Each time Luna tried to get a word in, the pony, Linda, would move on to something completely different, impressively speaking without punctuation and even more impressively treating the Throne of the Equestrian Diarchy as though it were beneath her. The returned princess tried to be patient, truly she did, but with the incessant dribble flowing past the mare’s lips, combined with her ridiculous head and neck gyrations and the fact that her eyes rolled into the back of her head as her mouth moved on autopilot, the antiquated instincts of yore crept back to the forefront of the alicorn’s mind in spite of her sister’s lessons on the sensitivity of today’s ponies. She grit her teeth in a futile attempt to quell her festering ire, but it was all for naught, as the mare began to speak about how no one ever accepted her back-hoofed compliments and gave her all the love and respect of a queen for the times she was, at best, a decent pony.
“And when I got my mane styled for the third time this week, the harlot cut my hair half an inch when I told her I wanted three-quarters of an inch! This isn’t even counting how or why the Imperial system even exists in this universe considering ponies shouldn’t use a ‘foot’ as a standard of measurement. Even so, she offered to cut the remaining quarter-inch off, but it was already ruined, ruined I sa―”
“I DON’T CARE!” Luna boomed, her Royal Canterlot voice shaking the room and causing Rainbow Dash to slam into a wall when she grasped her abused ears. “Nopony cares about thy wanton, rabid quibbles, nor thine obscene, vulgar beliefs of thy disenfranchisement! Simply because thou do not get thy way doth not a conspiracy against thee construct. The world will ne’er revolve around thee, so stop wasting Our time if thou hast nothing important to bring to Our attention!”
The mare’s eyes were widened, nearly popping out of her skull, but for the first time since she’d traipsed into the throne room all was silent. For a moment, at least. “I'd like to speak to your manager,” Linda demanded.
Luna’s eye twitched.
The door to the throne room opened and through it Linda was tossed out on her rear. The Lunar Guards shut the door with sighs of relief.
Luna placed a hoof to her temple. “By the stars, I’d rather spend another thousand years on the moon than listen to that mare prattle on maddeningly about nothing for another minute.” She opened her eyes. “Speaking of unwanted guests…” Rainbow Dash, in the middle of trying to sneak away, was teleported right in front of Princess Luna. “Loyalty,” Luna declared, her eyes boring into the pony who tried to make herself as small as possible. “Prithee, why art thou skulking about in the shadows like a common fiend? A sad attempt." Luna glanced at Rainbow's vibrant hair. "‘Tisn’t as though thou’rt inconspicuous.”
Rainbow Dash lowered her head between her shoulders, looking around to find that the eyes of every Thestral were on her before realizing she wouldn’t be able to escape from this sticky situation, at least not without some smooth-talk. “Um. Heh. I-I was… just looking for the restroom!”
Luna stared at Rainbow as though she had stupid all over her face. “The restroom,” she repeated, unimpressed.
Rainbow took a step back. “Yeah, I, uh, I mean, yes Princess! I was looking for the restroom! And if you’ll be so kind, I’ll be on my way and out of your hair in ten seconds―”
“Tell Us, Element Bearer, is it customary practice in these times for Our ponies to seek out the lavatories clad in black attire, with sound-nullifying spells o’er their hooves and face-concealing masks upon their heads?” She yanked Rainbow’s ski mask off, revealing her face for all to see. One of the Lunar Guards gasped, caught off-guard upon seeing who was underneath. The guard next to him elbowed him in the ribs.
Rainbow rubbed a hoof on her leg, looking bashfully to the side. “Um, yes?” Luna continued staring at her. “Okay, okay! It’s only because I’m shy.” Luna’s face of stone fell into a deep frown. “A-And it gets drafty up here. I get cold very easily.”
“Rainbow Dash, we are in the middle of the summer. I already have a migraine to temper, so enough excuses. Are you and Twilight Sparkle here for my sister’s prize?”
“W-Wha- How did you―?”
“You and Magic were speaking through an open window over the throne room, you ditz!”
Rainbow opened her mouth, raising a hoof, then shut it, lowering her hoof back to the floor. “Well, shoot. I am become error.”
“Indeed,” Luna deadpanned. “Should Tia catch wind of your machinations, what comes afterward is on your head, Loyalty. Do not say I didn’t warn you. Now get out of my sight.” As Rainbow Dash made herself scarce, Luna ordered one of her guards to fetch her an ibuprofen.
After a few minutes of wandering about, the sound-proofing spell having long-since dissolved, Rainbow Dash at long last arrived at her destination: it was a dark room, glowing with glyphs and runes, and at the center, on a pedestal, was a large chocolate cake. Rainbow scanned the room, wondering what the best course of action was. The room must have had top of the line security if Princess Celestia didn’t even bother posting her Royal Guard at the front. Either that, or she didn’t want them tempted to steal her delicious cake.
After a moment, Dash shrugged, throwing caution to the wind as she walked in a straight line to the delightful confection, tripping every alarm and erasing every rune in her single-minded path. When she reached the cake, she turned around to find that all the symbols were for show, and they didn’t appear to actually serve any purpose. All the security, it seemed, was dumped into the area immediately surrounding the cake. There was a hoof-print sensor, a guillotine, a badger, and a pit of scorpions. Rainbow Dash’s jaw dropped.
“Yeah, no.” With that, she produced from her saddlebags a thermite charge and melted through everything but the badger, because badgers are indestructible. With the badger on the loose, a problem she was sure she wouldn’t see the brunt of, Rainbow observed the cake for a long moment, moving her hoof ever closer at a slow pace before dropping the pretenses and simply snatching it off its perch. The room began flashing red as an actual alarm sounded, and a steel door began its glacial descent at the only exit to the room. Balancing the cake on her back, Rainbow galloped again over the glyphs, though this time the floor began to crumble and saws and snakes and sawsnakes rose through the cracks. She leapt, and spun and dodged and dashed, and in the end she slid beneath the descending door mere moments before it shut, the cake secure on her back.
She let out a haggard breath, her heart racing in her chest. A strand of her mane was also on fire, but she paid it no mind as she fought to regain her bearings. Her eyes snapped wide open when somepony giggled. Looming over her was Princess Celestia, a manic expression on her face. By her side was Twilight, looking down at the floor in shame.
“So good to see you, Rainbow Dash,” she said in a motherly tone, snuffing out the flame in Rainbow’s mane with magic. “Though I wish it were under better circumstances.”
“P-Princess!” Rainbow exclaimed. “This isn’t what it looks like!”
“Oh?” Celestia blinked. “So you’re not attempting to rob me of my cake?” She laughed, placing a hoof over her mouth. “Ah, what a relief that is! You realize stealing from royalty is a federal offense, so I’m delighted that I won’t have to send either of you to the dungeons.” Her smile remained when she lowered her hoof, but her eyes were cold. “However, given what Twilight, my star pupil, has told me, it’s quite the contrary…”
Rainbow's blood ran cold, and she slammed a hoof down to the marble floors. “Twilight!”
Twilight shook her head, tears in her eyes. “I’m sorry, Rainbow! The Royal Guard found me and threatened to arrest me if I didn’t come with them. I-I tried telling them I was only out for a midnight stroll, but they wouldn’t believe me.”
Celestia raised a brow at Twilight, the unicorn cowering beneath her gaze. “A midnight stroll, Twilight? On the roof?”
Twilight quivered. “I… took a few wrong turns?”
“You and Rainbow Dash do realize that a few wrong turns can land you in a cell, correct?”
Rainbow pointed a hoof at Celestia. “Y-You’re crazy! We’re trying to make sure you don’t ruin your diet and you nearly killed us!”
Celestia waved a hoof. “Details, details.” Her smile returned. “And a count of lèse-majesté on top of the charges of treason, trespassing, and attempted robbery. And as for you, Twilight—” She shook her head “—I expected far more from you, my little pony.”
As a number of Royal Guards advanced from both sides of the corridor, Celestia took a step back. “Allow this to be a lesson for the both of you. Perhaps a couple hundred years in prison will teach you respect.”
“WHAT!?” Rainbow and Twilight shouted in unison.
“What?” Celestia asked. “It’s not like that should be much of a surprise. I’ve given harsher punishments for less.”
With that, Celestia cackled as the two mares were shackled and dragged off to the dungeons, never to be seen or heard from again. At least, until the next monster showed up.