In the moonlight, a small, gray pegasus was lying on a bed in a spare room in the Canterlot palace. She slept peacefully, dreaming of a world of Muffins and Bubbles across green rolling hills and a background of blue skies. She pranced and danced around before soaring high into the bubbles. She had never felt more alive than right this moment in time, well, there was one with the Doctor, but that was beside the point. In fact, she could swear she could hear him right now, calling her name. She stopped on a muffin that had been floating nearby and listened hard, trying to hear him.
"Deerpy! Wake up! Quick! Wake up!"
The muffins exploded into nothingness, leaving Derpy starring off into the moon.
"Derpy! Quick! We need to go!"
"Why?” she said sleepily getting up, "Is the palace under attack?"
"What? Heavens no!" exclaimed the Doctor, "But we need to go somewhere!"
"Where?" she asked before he grabbed her
"To the TARDIS, and a thousand years in the past!"
"What? We already went there! Why do we need to go back?" yelled Derpy as the Doctor carried her through the halls to his TARDIS.
"Eris! That's why!"
"She's a crazy psychotic pony-thing who is in love with Discord. What else do you need to know?"
"What else do I need to know?" came the Doctor, stopping and turning to his assistant, "She said it was Chaos and Disharmony and that it's not supposed to make sense!"
"Well, yeah it's not." answered Derpy
"Exactly! Why? Why does it not make sense? Even Discord made sense! He wanted power, and he thought all the Disharmony was funny. She, she's just doing it to because she's plain crazy!"
"Yeah, she's crazy! Crazy doesn't make sense!" yelled Derpy at the top of her lungs
"And we are going to find out why! Come on!"
He took off again despite protests from Derpy. She let out a cry of frustration and followed after him.
The TARDIS was parked just outside in the main Palace garden, with the Doctor already setting coordinates into the complex machine.
"Now, answer me this," came Whooves, “When did we first meet Eris?"
"A couple of hours ago?" was Derpy's response
"No, no, no, the first time!"
"We didn't. We saw Scrapper seal her in!"
"Exactly! Eris was frozen in ice when we saw her, but why?”
“Because she's a insane Pony-thing! I told you that already!”
“Why did she become a insane Pony-thing!? Why is she so blind to do Discords bidding? How was she created, and why did she wait so long to strike? If what Scrapper is saying and he sealed her a thousand years ago, why did she wait until after Nightmare Moon left?"
"Because Princess Celestia and Princess Luna were powerful and defeated him, so going up against them would silly."
The Doctor stopped what he was doing and looked to Derpy in surprise.
"Bloody brilliant! Amazing Derpy, I completely missed that fact! Still, that’s only half the answer. That just wont do! Off we go!"
The TARDIS came to life as it powered up and started to travel through time and space once again.
"Off to where, good Doctor?" came a voice both recognized
"What?" yelled Whooves
"Princess Luna!" cheered Derpy
"What?" came the Doctor again
"Hello Miss Hooves. I see you and the Doctor are on another adventure."
"How did you...?"
"And you get to come on one too!" cheered Derpy
"Seems that way!" replied Luna happily
"What?" said Whooves as he stepped in between them, "With all due respects your majesty, how did you even get in here?"
"I saw it sitting out here, and decided I wanted to see it from the inside. It's a lot bigger than I thought."
The Doctor looked at her, his mouth agape, when his brow furrowed down and he clenched his teeth in anger.
"You planned this didn't you?" yelled Whooves, but it wasn't to Luna, or Derpy, "Is this payback? Payback for attaching that one device so I could track those particles!?
"My good mare, what is he doing?" whispered Luna
"He's, talking to the TARDIS." whispered back Derpy
"Does it talk back?"
"Huh? Decide to let some random stranger in without my knowledge?"
The entire ship rocked back and forth, only throwing Whooves off balance.
"Alright, alright, I get it! No more strange panels without your permission." he yelled walking back in between the two mares,
"Can you believe that? I tell you she takes human form once and she get's an attitude from it."
He grabbed a hammer and then walked back to the console, "An attitude!" he yelled, "Well, since we are in the presence of two ladies, and Royalty for that matter, can we please go where I set you to go?"
With that, a lever threw itself with a bang.
"Thank you!" yelled the Doctor as he hit a panel with the hammer
Luna looked to Derpy, hoping she had an answer for her.
"You get used to it." was all Derpy could give
"Right then, a thousand years in the past, tell me Princess, was it lovely then?"
"I was Nightmare Moon, you tell me."
"Riight....didn't take that into consideration. Guess the palace would be the safest place. To the Royal Palace!"
Two more levers threw themselves and the Doctor himself tossed his hammer, hitting a button dead on.
"Doctor, why the Royal Palace?"
"Simple, really. Eris, sensing the weakness of the Princess sisters thanks to Nightmare Moon figured now was the time to strike! The best way to under stand her mindset is," he yelled happily pushing a button, "to be right where she wanted to be!"
The TARDIS bucked and jerked traveling through the time stream, much to the Doctors joy.
"We'll be landing shortly your Highness! Time travel is quicker than you think!"
The TARDIS buckled again, much to Luna's discomfort, and Derpy's delight. Seeing that the gray pegasus was having much more fun in the air, the Alicorn took flight just as the whole ship bounced again. The TARDIS roared as it began to settle into the current time stream.
"Tell me Doctor, you do this all the time?" yelled Luna
"Not all the time, just most of it!” The Doctor yelled back
The TARDIS eased up as it landed, and a jet of steam poured out from above, and right onto the Doctor.
"Yes, yes, you are literally venting on me!" remarked the Doctor as he began his walk to the door, "I get it! I'm sorry. It wont happen again."
He opened the doors revealing a bright, lush green forest, covered in the air by pink clouds.
"Right, welcome to Canterlot Royal Palace, or where it's still being built."
He opened the door to see several construction workers in old uniforms working to set up the halls that would soon be the gilded palace. Royal Guards stood before them and watched them, making sure to keep a keen eye out for intruders.
"Very well then," announced Whooves, "It's a bright sunny day! Time to start investigating!"
The moment his hoof stepped on the ground, it suddenly shifted to night.
“I did not do that.” answered Luna
“Celestia must have tried to bring about the night on her own.” said Derpy
"Right then, It's a beautiful and peaceful night! Time to start investigating. Come along Derpy, and uh..... well, after you your Highness. Oh.... hmm, we do have a problem."
"What is it Doctor?” Luna asked
“Well, look at you Princess? Remember Nightmare Night?”
Luna remembered to that fateful night, and had generally pleasant memories from it. The concerned look from the Doctor reminded her of the beginning of it.
“Oh.... I see.” she said, realizing her predicament
“We can't have you walking around like that.” spoke Whooves pondering, “Nowhere in Equestrian history did Princess Luna reappear a few days after her banishment.”
“Hmm...” thought Luna turning away
“Well. Maybe she could stay in the TARDIS.” said Derpy
Whooves shook his head and shivered in fear: “No, no telling what she could accidentally bump into in there.”
There was a flash behind them that neither bothered to notice.
“What? Dinky, Dizzy, and Sparkler go in there all the time!” explained Derpy
“Well, I trust them!” answered Whooves
“Aside from Sparkler, you trust my two little Fillies over the Royal Princess?”
“Well, your two Fillies,” he tried to say as a bucket of paint floated past him, “Well, I know them.”
“You know Pinkie Pie as well and you won't let her near the TARDIS without somepony with her.”
“Well, Pinkie Pie is not your filly.” responded Whooves, very 'matter-o-factly'
Derpy looked at him in the usual way when he thought he made sense as a red neckerchief floated past her as well. She stomped her hooves in anger and Whooves smiled nervously.
“I just don't like random mares walking in and around my TARDIS. I mean, it's my TARDIS!”
“This is the younger Royal Pony sister! The Princess of the Night! She's just not some random mare!”
“Ready!” said a strange mare from behind.
The two looked to see a small light blue Pegasus standing there with purple colored hair and a red band around her head. She smiled and posed a little, giving off her Cutie Mark, a single crescent moon.
“Just call me Moonbeam.” she said Happily
“Princess Luna!?” came a astonished Whooves
“Wow, you look great!” Said Derpy with a surprised look on her face, “I didn't know you could do that!”
“I learned a few tricks as Nightmare Moon. Transformation is foals play for me. Shall we?”
She stepped in front of the two amazed Time travelers and looked around. She could recognize what would soon be a few new rooms when suddenly, a Royal Guard Pegasus stopped them short.
“Halt! Who goes there!”
He eyed them down from behind her armor. Luna was about to announce who she was when she realized it and stopped. She backed down a little wondering what to do when Whooves came to her rescue armed with his psychic paper.
“Canterlot Palace Inspection team! I'm Mr. Tennant, this are my assistant Miss Hooves, and Moonbeam, the Palace Interior Decorator!”
The Guard looked at the paper and shook his head.
“Alright. Don't stay long. Since it's apparently night now it wont be long until closing time.”
“Yes, of Course! Come along now!”
The three walked away and soon Whooves and Derpy were looking around for any signs of their target. Luna, meanwhile, was marveling at the construction of the palace and remembered when she and Celestia were just joking around and trying to make a better Palace design to their current one in Everfree before it was destroyed. She never noticed it before, but a lot of the architecture was based of her own additions to Celestia's paintings. As she did, she wandered off down a hall away from the other two, oblivious to that fact. Fortunately, Whooves caught sight of her.
Luna turned around to see them standing there behind her.
“This way!” said Derpy
“I know my way around the Palace!” she replied, “I'll catch up later!”
“Okay!” answered Whooves, “On we go!”
“Are you sure your okay on you own Princ-err, Moonbeam?”
Luna nodded yes happily.
“What could go wrong Derpy?” asked the Doctor as he walked on
“With you around, a lot.” replied Derpy
Whooves grunted something out of earshot, but he let the comment slide. Luna returned to her walk, smiling at the various works that were completed or being completed. Even in the light of the moon, the palace looked splendid. Looking up the the moon, the idea that she was there, right now, fuming as Nightmare Moon made her shudder in fear. Remembering to all those cold lonely years... Lost in her memories, she didn't look ahead and bumped into another pony.
“Oh, I'm sorry! I wasn't looking where I was going.” she apologized
“No trouble at all.” said a voice Luna recognized
She looked up to see the flowing hair and marshmallow skin of her sister, Princess Celestia. She stepped back in shock upon seeing her sister here, not looking just like she remembered before being imprisoned on the moon. Of course that difference was just the flowing pink hair. Celestia, saw this and just smiled.
“It's alright. Tell me, who are we to make the acquaintance?”
“Uh.....” stammered Luna, both at seeing her sister, her use of the Royal We, and other obvious reasons, “Moonbeam.” she said finally
Celestia gave out a sad sigh, remembering to her sister locked in the moon, but recovered and smiled at the disguised Alicorn.
“Pleased to meet you. Tell us, what is that you do here?”
This time Luna was ready: “Palace Decorator.”
“Hmm, a new one they let on?”
“Yes.” answered Luna
“Hmm, why don't you show us around and give us some of you insight?” asked Celestia
“Sure!” said Luna happily, “I'd be happy to!”