//------------------------------//
// Nightmare Night 
// Story: The Doctor Screws Up Equestria 
// by a human 
//------------------------------//

"I am going to make you an offer you cannot refuse. If you accept, you will get all the power of the throne."

"And if I refuse? What's the catch?"

"The catch is," she smiled, "if you refuse, I will kill you."

– – – –

The Doctor was the most skilled time traveler in the universe. At least in theory. In reality, most of his knowledge was useless here inside the time bubble. The TARDIS could no longer accurately display what year it was, which was a huge problem given that it could never accurately steer.

Another problem was that, to the best the Doctor and Derpy could figure out, the timeline of this world followed anything but a linear pattern. Often they would go, at least from their perspective, careening through time and space only to arrive at the same town next year. Except that one random detail would be different, like the ruler would be different or everyone would be gay. The only constants, they could gather, was that there was always a town called Ponyville, and the land's ruler seemed to ricochet between two ponies named Celestia and Luna. Furthering the mystery, there were some parts of the timeline that the TARDIS almost refused to land on, and whenever they managed to, they found the planet a scarred wasteland.

Eventually the Doctor and Derpy reached the conclusion that in order to figure out anything about this world they would need to stay in the same place for at least a month, so they, out of options, landed the TARDIS somewhere completely random and went out to explore.

They had stopped on a holiday, a good sign.

"Welcome," a spastic blue pony yelled, "to Nightmare Night!"

"Oh," Derpy said, looking around, "are we supposed to be dressed up?"

"I don't know," the Doctor said. "Are we supposed to be dressed up?"

Derpy put her hoof on her chin. "I think this is like a holiday I had back home. We're supposed to be in costumes. We can be dressed as fictional characters, stereotypes, or prostitutes."

"Oh." The Doctor thought about it. "Well, we can just say were dressed up as time travelers. That's a stereotype, right?"

"That's stupid."

"We'll fit in."

Derpy raised an eyebrow. "What do you know about fitting in?"

The Doctor couldn't argue with that.

"Be back in a bit," Derpy said, running off. "Try to have fun without me, okay?"

"Hey! Where are you going!?"

Derpy stopped. "To the TARDIS," she said, "obviously. That thing has a huge costume rack, doesn't it? I'll be just a second, trust me." She waited for an objection, and when the Doctor failed to articulate one fast enough, flew off.

The Doctor really didn't like it when people treated the TARDIS like a giant clothesrack, but he figured if he had time to worry about things like that life couldn't be too bad. 

He walked around, trying to enjoy the festivities. One benefit to being trapped in the time bubble was that death no longer appeared to follow him wherever he went. Usually, that would be great, but knowing every timeline in this world inevitably led to him facing the most horrific evil he had ever faced made it hard to see any good parts in his situation.

It also made him terribly paranoid. After rescuing another kid from another eldritch alien conspiracy that turned out to be bobbing for apples, the Doctor sat dejectedly on a bench that looked slightly more pathetic than he was feeling.

"You are the time traveler, are you not?"

The Doctor froze. It was another conspiracy theorist, he was sure of it. This never ended well. He slowly turned around, slightly delaying the inevitable.

A large blue pony was staring at him intently. He recognized her as the one shouting earlier. She had large made-up eyes that, after years of social isolation, were closed at just the wrong amount to make conversation comfortable. Her mouth was closed, frowning. She wasn't breathing, but she wasn't holding her breath either. If she was moving at all, it was imperceptible, and if it wasn't for her occasionally talking, it would be difficult to tell she was alive. 

But more importantly, the Doctor had the vaguest feeling he had seen her before. Not just a couple minutes ago, when she was yelling, but somewhere else. Somewhere on his travels.

"Have we met?"

She looked confused. "I do not think so. But you might know of me."

"Really?"

"Have you ever heard of of Princess Luna?"

"Yes."

"The Princess of the Night?"

"Yes."

"Do you not know what she looks like?"

"No."

She looked disappointed. "Why not?"

"I assumed the Princess of the Night was a porn star."

Her eyes widened and brows furrowed. "She is not."

"How do you know?"

"Guess."

The Doctor stared at her a bit, then it finally came together. "Wait, you're…"

She smiled. "Princess Luna."

One of the rulers of this land! The Doctor gaped. He had hundreds of questions, but wanted to get the most important out of the way first. "Okay, so how did you know I'm a time traveler?"

"Well, you keep appearing throughout history with the same face," Luna said. "That means you are either a time traveler or immortal, and you cannot be immortal."

"Why?"

"Because I know all the immortals in this world."

The Doctor sighed. "Just give me a straight answer for once," he said. "I know you must tell everyone you're immortal, but what's the truth?"

"The truth?"

"Look, I've been around, and you would not believe the amount of people I've heard say they're immortal. And you know what? Every single time it's been a lie," the Doctor said. "Why? Because it's impossible. Living forever? It goes against the basic principles of the universe. Conservation of matter. All that stuff. Nothing lasts forever. Not even the universe. So out with it."

"I am immortal."

"Really."

"I have lived for millennia, watched civilizations turned to dust in my wake."

"So have I," the Doctor said. "I still can die."

"Explain my hair."

It was slightly, imperceptibly wrong. Actually not. It was very perceptibly wrong. It was as if a two-dimensional object had been hastily pasted into a three-dimensional reality. It was difficult to say for sure since it was constantly moving, wafting away from her head like a pillar of smoke. Inside there was a full set of constellations. Someone could probably spend years making a celestial chart of them if they weren't in someone's hair, thus making the process very embarrassing, and most definitely not something one of the princesses made some poor cartographer do for years as a brutal punishment. Truly only a supremely unnatural beast could have hair like this.

"I've seen worse."

"Nevermind, it does not matter," Luna said. "The important part is, may I time travel with you?"

"What?"

Luna blinked. "That was a bit abrupt, I think."

The Doctor was more than a bit taken aback. "A bit?"

"But still. What do you say?"

The Doctor didn't even have to think about it. "No."

"Why not?"

"It's my golden rule."

"What?"

"Anyone who wants to time travel that badly is probably going to end up causing a paradox."

"I will not. I swear on my honor as a princess."

"And they probably have a political motive."

"I do not." Luna shuffled around awkwardly. "Maybe."

"Yeah," the Doctor said, getting up, "I think you can see the problem."

"Pretty please?"

"No." He started off before getting predictably stopped.

"Wait!"

The Doctor turned around slowly, making it as clear as possible he was irritated. "What?"

Luna put a hoof to her ear. "Do you hear that?"

"Do you really think I'm going to fall for that!?"

"No, really. It sounds like… keys against metal."

The Doctor's eyes widened. "What?" There was only one thing that made that sound. The TARDIS. He listened closely.

Faintly, in the distance, he heard it.

"Derpy!" the Doctor yelled, and sprinted off towards the TARDIS.

Luna smiled.

– – – –

It must have actually been keys against metal because the TARDIS was still there.

"Dammit," he said, "I knew I shouldn't have trusted her." He knocked on the front door. "Derpy? You in there?"

No response.

"I'm coming in."

He grabbed the front door and tried to pull it open.

Locked. 

And he forgot his keys inside.

With a sinking sadness, the Doctor realized he had locked himself out of the most powerful and well protected ship in the universe.

"Derpy!?" The Doctor yelled, banging on the front door. "Derpy, if you're in there, open up! You hear me!? Open up!"

No response. She was either already outside, and hopefully had her own key, or she was inside and had been crushed by the giant clothing rack. The Doctor hoped for the former.   He ran back to town. 

While running, he heard a bang, like a gunshot. He turned around and saw a green explosion in the air. Dismissing it as fireworks, he ran along.

– – – –

"A blonde gray pegasus? Can't say I have."

"Haven't seen anyone like that."

"Googly eyed? What do you mean, googly eyed?"

"Sorry, no dice."

No one had seen Derpy. That wasn't good. She could be anywhere, and she had a TARDIS key. That was dangerous. In the wrong hands, someone could… not do much, since they were in a time bubble, but it would still inconvenience the Doctor, and he didn't like that. 

Right when he was beginning to lose hope, someone tackled him to the ground.

"Ow…" he groaned, rubbing his head.

"Sorry!"

The Doctor looked up. It was Derpy. Dressed as a pirate. The Doctor wondered how none of the townspeople had seen her, but in the end decided to ignore it.

"Where have you been?" he said.

"Looking for you," she replied. "What have you been doing?"

"Do you have your TARDIS key?"

She produced it. "Yeah."

"Oh thank god," the Doctor said, wiping his brow. "I thought I locked myself out."

"You can lock yourself out of a TARDIS?"

"Yeah. Shut up."

Near the forest, a crowd was starting to gather. A pony in the center was gesticulating wildly, obviously trying and failing to calm things down.

"Do you think something is going on?" Derpy said.

"Let's find out," the Doctor said.

They walked over to the scene and worked their way into the crowd.

"What's going on?" the Doctor asked.

"They found something in the forest," someone said. "I think it's a body."

The Doctor and Derpy pushed their way through the crowd and reached the center. The pony in the center turned to them, angry.

"Nothing to see here," he said while gesticulating yet more, which was just making everyone more curious. "Just get back behind everyone else."

"Would you mind telling me what's going on?" The Doctor said.

"What business of it is yours?" the pony said.

The Doctor produced his psychic paper. "I'm Inspector Smith. This is my assistant, Doctor Doo." The pony read god knows what on the paper and nodded in admiration. "What appears to be the problem?"

"We just found a corpse in the forest," the pony said. "And it isn't pretty. Follow me."

He led them through a winding path in the forest, obviously familiar with the area. It was late at night, and the forest pitch black. Finally, they reached a small clearing that was cordoned off with some makeshift tape. The Doctor recognized the area as being near the TARDIS. A body was covered by a gray sheet.

"You might want to brace yourself," the pony said. "This is a bit unpleasant."

"I've seen my share of crime scenes," the Doctor said.

"I wasn't talking to you." He looked at Derpy.

She gulped. After taking a second to compose herself, she nodded to the pony. He removed the sheet.

The worst part wasn't that the corpse's face was permanently locked in terror. The worst part was you could tell even though the face was utterly mangled beyond recognition. The cutie mark was also similarly mangled, making recognition impossible. There were bruises on the torso and what looked like a burn mark on the head. The victim might've used to have wings, but the skin there was ripped so thoroughly it was impossible to know. Next to the rips were what appeared to be bite marks. The sheer amount of injuries made it difficult to tell which was the fatal blow.

The other strange thing about the corpse was that, if she wasn't standing right next to him, the Doctor would've sworn it was Derpy. The colors and build were exactly the same.

Derpy noticed too.

"Is that… me?" she whispered to the Doctor.

"That's impossible," the Doctor said. "You're right here."

"But could that be… me in the future or something?"

The Doctor paused. He wished he could tell. "I don't know."

The pony grew impatient. "Well? What are your conclusions?

"This must've been a professional job," the Doctor said. "The evidence has been erased too thoroughly. Anything that could be used to identify the victim has been removed. No common criminal would have the means or wit to do that."

"That's exactly what we thought," the pony said. "We'll be taking this back to the lab as soon as possible. Hopefully that'll let us catch the culprit."

At that, someone else ran up, panting.

"What? What is it?" the pony said.

"It's Princess Luna, sir," they said. "No one can find her anywhere!"

"What!?"

– – – –

The whole town began frantically searching for her to no avail. A panic was beginning to set in.

"Shouldn't we let the royal court know about this?" the Doctor said.

"Would you want your town known as the town that lost a princess?" someone yelled back.

The Doctor shrugged and continued to aimlessly run around. In desperation, people were checking inside houses, inside trash cans, under benches, in that fold in space time where Pinkie Pie stores all her crap, inside drawers, and thousands of other places the princess was unlikely to be, but everyone felt should be checked so they could testify they were thorough in court later. 

Still nothing.

So it was a bit surprising when, after a couple hours, the townspeople saw the royal chariot fly through the air with Luna on it.

It landed and she calmly stepped out.

"Where were you!?" someone screamed.

"My apologies," she said. "I had some urgent business to attend to."

"Urgent business!?"

"Urgent royal business."

"Urgent royal business!?"

"And thus secret."

The town was silent.

"I bet she was just screwing her guards," Derpy whispered to the Doctor.

The Doctor looked at her like she was insane.

"Well, don't let my brief absence ruin things!" Luna yelled. "Let the festivities… resume!"

The town gave a forced cheer and dispersed.

Noting that he was one of the few that stayed behind, Luna leaned over to the Doctor. "Okay, what's really going on?" she said. "They couldn't have been that worked up over me being gone for a couple hours."

"Yes, they could," the Doctor replied, "but you're right. Someone found a corpse in the forest. A murder."

"A murder!?" Luna yelled, then looked around to make sure no one heard. She turned to her guards. "Fly around and arrest any suspicious characters! The murderer might still be near!"

Her guards obliged.

"What makes you think that?" the Doctor said. "They probably knew the forest, and if they're a pegasus they're long gone."

"It's better than doing nothing. And they need something to do," Luna said. Her eyes softened. "Thank you. I'm sure anyone else would have tried to hide this from me. What was your name?"

"What? I thought you knew."

"Why would I know?"

"We just talked a few hours ago."

"We did?"

"And you seemed to know more about me than I did."

"I did?"

"Oh, the princess is just groggy after her royal business," Derpy said. "Right?"

Luna looked confused. Then a bit angry. "Yes. Apparently."

The Doctor just looked confused.

Suddenly, a flash of blue light flashed above the forest. It reminded the Doctor of the green explosion he saw earlier.

"That must be one of my guards," Luna said, extending her wings. "He must've found someone. Let's go. Hop on."

The Doctor paused uncomfortably. "Me?"

"You look competent."

The Doctor grimaced. "You want me to… get on you?"

Luna looked a bit offended. "Is it that strange?"

"No," Derpy said, "it's my job."

The Doctor gaped at Derpy, slack-jawed. Then he jumped on Luna's back.

"Hey, what gives!?" Derpy yelled.

"Derpy," the Doctor said, "take a cold shower."

And they took off. Derpy pouted.

Luna chuckled. "This is ironic," she said.

"What? Why?"

"No reason. Hold on."

She banked to the right and and swooped down. It was all the Doctor could do to stay on. With considerable effort, he managed to look ahead and see what she was racing towards. He saw one of the bat ponies in hot pursuit of an earth pony on the ground. The earth pony was running with all his might, but against two skilled flyers, one of them a princess, he stood no chance. 

There was only one way to deal with a situation like this.

"Yell at him," Luna said.

"What!? Why!?" the Doctor screamed, the Gs blasting him in the face.

"It will make him feel even more outnumbered."

The Doctor didn't have enough time or energy to argue. "Stop it now! Cease and desist!" he yelled. "We have lethal force!"

Luna looked back at him, panicked. "What!? No we don't!"

"Yes, we do!" the Doctor said. "Just hit him hard enough!"

"That wouldn't kill him, just stop him!"

"Well then even better! Do it!"

"Oh. Right!"

She swooped and tackled the fugitive to the ground.

"On behalf of the royal court, I'm putting you under arrest," Luna said.

The fugitive laughed. "You're not the princess."

"You're right," Luna said. She leaned in, scratching his face with her horn. "But I'm one of them now, and that's all that matters."

He folded. "It… it wasn't my fault! She made me!" he yelled.

"So," the Doctor said, jumping off of Luna's back, "you're the one that killed that poor mare?"

"…yes."

"Tell me," the Doctor said, "who was she? What was her name?"

"What do you care!?"

"It might be someone I know."

"That's impossible."

"Just tell—!"

Luna put a hoof on the Doctor's mouth. "It's better you don't know."

Usually the Doctor would have objected, but when he looked into her eyes he gave up immediately. It was unlike him, but he saw something in them. Something he hadn't seen the first time he talked to her, and which the sudden presence of disarmed him.

Compassion.

– – – –

Derpy was leaning against the TARDIS, clearly bored. "So? Did you catch the guy?"

"Yeah."

"Well, what happened?"

"He was just some maniac who murdered his ex. I don't want to talk about it."

"Okay."

They stood there awkwardly for a few minutes before the Doctor noticed something.

"Derpy. You're not breathing."

"What?" Derpy looked down at her still closed mouth. Then she made a big show out of inhaling deeply. "Oh, silly me! I forgot."

The Doctor stared at her uncomfortably.

Something strange was going on, and he hoped he was very wrong about what it was.