Luna woke up to the rising sun, yawning and stretching away the stress of a night of policing dreams. She got up as she always had, trotting to the bathroom door and opening it with her magic to waltz in and get ready for another day.
Except, this time the door didn't open. Instead of swinging inwards to the bathroom, it refused to budge, and Luna walked straight into the elegant door, facefirst. "Ouch! What is the meaning of this? Is this door broken?" She asked aloud. So she pushed on the door, throwing all her weight into it while ensuring the knob was turned, but it wouldn't move, even a tiny bit. So, needing to go to the bathroom, Luna resorted to plan b: magic blasts. If it wasn't for the soundproofing on her room, the guards might have thought the castle was under attack, but at the very least Luna was able to relieve herself. Then, irritated but still in a decent mood, she walked through the doors of her room and into the hallway.
Or more specifically, she tried to, for those doors failed to budge either.
"What in Tartarus is going on today? Is every blasted door in this castle stick this morning?!" She pulled the doors with all her might, but nothing. Deciding to not scare anypony in the hallways, she dropped the soundproof spell and called out. "Guards, our door seems to be stuck on this side. Couldst thou try and open it from your side?"
"At once, Princess!" The two guards attempted to push the door inwards, but they too found it impossible to force the door open. In a final fit of desperation, Luna teleported through the door to save face, and ordered the guardsponies to find out what was wrong. Suddenly, there was a magical explosion from the dining hall, and Luna rushed to investigate.
What she found was a very irate Celestia, the main door to the dining hall in splinters, and maids scrambling to sweep up the mess. "Good morning, dear sister," Luna remarked. "Seems that our room was not the only one with this issue."
"Luna! I didn't see you there. For some reason, none of the doors in the castle are opening! I've sent out a call to our best repair ponies to help solve the issue. But for now, I'm afraid that dismantling the doors seems to be the only option. Try to break as few as possible, but we do need to open a few doors to allow our little ponies who cannot teleport through them. After breakfast, at least. Come on, let's eat, and then we can work on helping everypony out.
"I'm sorry your majesties, but I'm afraid I don't understand what you are asking me to do. All of the doors seem to work fine, aside from the ones you have already smashed.
"Nonsense! None of them work!" Remarked Luna. "Oiled Hinge, we demand that thou show us these supposed working doors!"
Oiled hinge had seen a lot to door problems in his day, but how the princesses were acting about the doors in the castle was new to him. And he had been working for thirty years! "Luna is right, something is wrong with the doors. Observe," Celestia remarked, having led the group to the doors to the ballroom. She leaned up against the door, pushing with more than enough force to force a door like that open. "Now, how is it you claim they all work?"
Oiled Hinge looked at the royals, confused. "You... that is to say... uh..."
"Well? Out with it!"
"Maybe I should just show you." And with that, he pulled the door open.
"...when we find who is responsible for this, there will be some words."
In an undisclosed location, two figures watched the show through a crystal ball. Both were obscured by shadows, but both were clearly biped. One was apelike, the other a mix of parts from dozens of animals. They fist bumped calmly in celebration.
"I can't believe that worked."
"Nick, mah boi, a good laugh is what all pranksters strive for."
"Did you just reference-"
"Still, I didn't expect them to break half the doors in the castle! Who would have thought that switching the way the doors swing would create so much chaos?"
"I figured it might. Thanks for helping with that, by the way. Hey, show me Blueblood stuck in his room again!"
Suddenly, the lights clicked on, revealing their secret meeting place to be the broom closet of Twilight's castle. "How about a swim in the moat instead?" Asked an irate Purple princess.
Nick ran off, but Discord pulled a dessert from nowhere and prepared to throw.
"Twilight Sparkle, you dare bring light to my lair! NOW, YOU MUST PIE!"