//------------------------------//
// Part One: Mistaken Identity 
// Story: The Two(ish) Doctors 
// by The Minister of Scones 
//------------------------------//

“Be careful with that, it's a precision instrument!” The Doctor was sitting in the middle of Ponyville's main street, watching Twilight magically steering a large blue box around a corner into the main street. She was visibly worn out, beads of sweat materialising on her brow as she struggled to maintain the magical aura.
“I'm doing the best I can!” she complained. “What is this thing? It seems to occupy two completely different sets of spacial dimensions!”
“Oh, five at least… careful!” Twilight had just let one corner of the box brush against the ground – not enough to do any damage, but enough to send a panic stricken look shooting across the Doctor's face, and to make him nervously tap his forehooves together. “That's vintage! There isn't another TARDIS like it left in the universe! Do please be careful!”

What was the Doctor doing, here in Ponyville? Well, simply put, the Timelords had unexpectedly decided that the Doctor was senile, which he wasn't best pleased about. They had decreed that he should be forcibly retired to the land of Equestria, where, they thought, he would be kept out of trouble. They had forced him through a regeneration (incidently, he was now in his twenty-second body, and looked far younger than he felt), and sent him and his TARDIS spinning straight towards Ponyville, having 'forgotten' that in his weakened state following the regeneration he would be in no condition to pilot her. He had therefore messily crashlanded in the woods near Fluttershy's house, and been rescued by the owner, who had then secretly nursed him back to health. The Doctor was very cross about being exiled, as he thought there would be nothing to do. On his first day out of the house, he had foiled an invasion attempt by the Nestenes and their Auton drones. This is called 'Sheer Dumb Luck'.
The next day, Twilight had happened to mention that there was a pony who looked and sounded almost exactly like the Doctor, and who went by the same title, who had lived in Ponyville for several years. The Doctor had been pretending to be worried about this ever since. In fact, he was rather excited. Who said exile was boring?

“You know, Doctor," hinted a disgruntled Twilight, "I think this would be a lot easier without an audience.”
“Why, are ponies watching?” The Doctor cast a quick glance either side. “No, I don't think anypony but me is looking at you, old girl.”
“I know," replied the alicorn, wondering how anypony could be so insensitive.
“Eh? But you just said-”
“Look, Doctor, there's Derpy,” Twilight pointed out, relief cascading across her face, “you wanted a word with her, didn't you?”
“Oh, yes, she's the one who… which one is she, then?”
Twilight rolled her eyes. “You see that pony-shaped dent in that lamp-post?”
“Er… yes, there it is.”
“Look beneath it.”
Twilight went back to her levitation, while the Doctor strolled over to a grey pegasus mare - or at least as much of her as was protruding from the street - with a cutie-mark of a cluster of bubbles and an honestly-can't-be-bothered blonde mane.
“Good morning, Miss!” he sang out, cheerfully.
“Oh, good morning," came her muffled voice from the road. "Just a moment...” With practised ease, the mare prised herself out of a Derpy-shaped hole in the cobbles.
“Do I have the pleasure of addressing Miss Derpy Hooves?”
She gave him an odd look, head inclined to one side, and eyes – the Doctor noticed this for the first time – pointing in completely different directions. “I answer to many names,” she said, faux-mysteriously, then giggled. “Yup, that's me. Mailmare extrodinaire. Can I help you, Mr…?”
“Just 'Doctor', will do fine. I think you'd find my name rather difficult to pronounce. Besides, I can't quite remember it at the moment,” he admitted.
“Um… okay...” Derpy was obviously beginning to wonder whom she was talking to, and to wish that she wasn't. She was already glancing from side to side – probably, anyway; it was hard to tell. She peered closely at the stallion in front of her. “You do kind of look like the Doctor, but I don't think you're him. Are you okay there?”
“Ah, yes. Sorry, I should have realised there'd be an element of confusion. Allow me to explain.”
“Right…” Derpy struggled to bring her eyes into focus. It was always tricky after a crash. Before her stood… no, it couldn't be… could it? “You are the Doc!” Derpy brightened up, but then began to look confused again. “Why did you pretend not to recognise me?”
The Doctor was taken aback. “Hold on, just a moment. I don't recognise you. I only arrived here in town some two or three weeks ago, and I've been in hiding for most of that. I only ventured out of Fluttershy's cottage the day before yesterday.”
“But you're...”
“On that day, it was I who foiled the invasion attempt by the Autons that I'm sure you noticed.”
“Were they those dummy-things?”
“Precisely, I-”
“Did they come out of the Everfree Forest?”
“I'll explain later. The point is, yesterday I was enjoying a celebratory picnic with my friends when one of them mentioned a certain pony who looked and sounded awfully like me who lives in this town, and has done so for quite some time. She also mentioned that you would be the one to tell me about him. So here I am.” He beamed and gestured to himself, rather more proudly than Derpy thought necessary.
“So… wait… you're not the Doctor?”
“I can assure you that I am the Doctor, and have been for several thousands of years.”
“Doctor, have you banged your head? Was it in an experiment?”
“What? No! Look, just listen. I am the Doctor, and someone you know apparently looks exactly like me. He could be a future me, or he might just be a double, but I want to make sure… my dear, are you quite alright?”
Derpy was backing away, trying to get as far from this strange madpony as possible. “Look, I don't know who you are, but I have a lot of letters to deliver, and I really ought to get going. See you… maybe.” So saying, she scooped up her postbag, threw it on, and took off – rather more hastily than politeness dictated.
“Well, that wasn't particularly productive.” He wandered back over to Twilight, who had managed to get the TARDIS into the town square.
“Why do you want it here, anyway?” she asked huffily, mopping her brow.
The Doctor was plainly delighted. “I'm glad you asked! It's quite simple, really. The TARDIS feeds partially on chronon particles, and since part of her resides in the fourth dimension, she relies on them to make repairs. She's still in a bit of a state after I crashed her – fluid link broken, Zeiton 7 dwindling, you know – so she needs to repair herself. The town square is one of the weakest spots in the Space-Time Continuum for miles and months away, so it's an ideal spot for her to recharge and fix one or two little faults.”
Twilight looked slightly stunned by the barrage of information, but was obviously interested. “The fourth dimension? As in time?”
“Quite correct. Did I ever tell you what the name stands for?”
“You never even explained what it was.”
“Allow me to elucidate. She is a Type 40 Time-Travel Capsule, capable of traversing the universe in the blink of an eye, given fair weather conditions. My own personal vehicle, and oldest friend.”
“Friend? You mean it's – I mean she's alive?”
“Well, yes, in a manner of speaking. She has a bank of computers.”
Twilight waited expectantly; then realised this was all the explanation she was going to get. “This is fascinating,” she breathed, looking at the box with new eyes.
“A TARDIS: the essence of transport. Time And Relative Dimension In Space. Behold!” As he spoke, he pulled out a key and unlocked the doors, and on his last word, flung them open to reveal… Twilight gasped.
“What do you think?”
“But… it's bigger… I don't… the outside… how?”
“She's dimensionally transcendental.”
“What does that mean?”
“It means… well, to be honest, it just means that she's bigger inside than out. Look, the outside exists in the three dimensions of width, depth and height, but the inside exists in the dimension of time, and a relative dimension of space. That means you can have as much inside as you like, because it doesn't take up any room in the three external dimensions.”
“But wouldn't that mean that there are only two dimensions inside?”
“Time, like space, although a dimension in itself, contains many dimensions of its own,” pronounced the Doctor, as if reading from a textbook.
Twilight pondered this. As a good scientist, she felt that the best method of learning more about this 'TARDIS' would be her favourite: unbridled experimentation. “Can I go inside?”
“Best not.” The Doctor noticed Twilight's drooping ears, and patted her kindly on the head. “Well, I'm sorry, but it won't be safe in there for a good while, yet. Just look.”
He was right. Inside the TARDIS, all that was visible was a poorly lit room, full of once gleaming-white surfaces (now coated in mildew), jutting bits of what looked like coral, vicious-looking spikes of rusting iron girder, and broken computers with parts spilled all over the floor. Twilight couldn't make out any more, but there was certainly the crackling sound of electricity discharging itself into the air.
“Poor girl,” said the Doctor, sadly, “she's far too old for this sort of thing. All the console rooms have been meshed into one thanks to dimensional warping in the crash, and it's left her in a bit of a state. Imagine how you'd feel if your central nervous system tried to hide in your brain!”
“How do you know she's a female?” asked Twilight, not best pleased about being patted on the head.
“She's not female female. She's just a ship. All ships take the feminine.” The Doctor slammed the door shut. “Now then, I need to find that Doctor fellow. Know where he lives?”
“No, sorry.”
“Why ever not? You're the princess, aren't you?”
“Well, yes, but...”
“Never mind. I'll just have to make discrete inquiries.”
Twilight sighed. She had an awful feeling that these inquiries wouldn't be as 'discrete' as the Doctor hoped.

“Doc! Doc? Let me in!” Derpy hammered at the door of her good friend the Doctor with an urgency born of confusion and worry. She had flown over (via one or two lamp-posts and a fence) as soon as she'd finished her deliveries for the day. Now she was panicking, wondering if she should have come sooner.
“Hold on!” came a muffled voice from indoors. The door flew open, and a rush of black smoke caught Derpy full in the face. She coughed and spluttered a little, and was overcome with dizziness; and then strong hooves grasped her shoulders, hauling her inside.
“Ditzy! My dear, how are you?”
Derpy – or Ditzy, depending on which of her parents you believed – looked up, and saw with relief the smiling face of the Doc, full of kindness and – thank Celestia – recognition. “Doc! You're okay!”
“Well, my attempts to turn a cockroach invisible have ended in disaster… again… but yes, I'm perfectly fine! Shouldn't I be?”
The smoke was beginning to clear, now that the door had been opened. Derpy looked around the familiar laboratory, full of the usual half-finished experiments and scientific paraphernalia. Clocks ticked (not all in the right direction), chemicals bubbled, electrodes buzzed angrily.
She thought for a moment, wondering how best to phrase her question. “Well, have you seen me yet today?”
“Not that I recall.”
“Then that wasn't you in the town square this morning?”
“Well, I've been busy in my laboratory all day, so unless my time-travel machine starts working and sends me back to this morning, then… no. Hold on,” he added, scratching his chin, “what wasn't me?”
Derpy swallowed. “There was some strange pony calling himself the Doctor, and he came up to me and said a lot of stuff about… Autons, and things. I thought he was you, but then I figured he wasn't, so I flew off… and he wasn't you, was he?”
“No, no.” The Doctor smiled and ruffled her hair. “I'm here. What convinced you he was me, then?”
“Well," began Derpy, feeling rather foolish, "he looked exactly like you. He sounded kinda similar, too.”
“Great whickering stallions!” The Doctor's voice took on a little more urgency. “Exactly like me? You're sure?”
Derpy nodded.
For a moment, a sadness passed across the Doctor's face. Then he was back to normal, his reassuring smile present once more; yet when he spoke, his voice was tinged with regret. “Well, that was only to be expected, after a while.”
“What do you mean?” Derpy's worry was apparent.
The Doctor sighed, and looked long and hard at her. It was a look full of melancholy, and Derpy's heart went straight out to him, although she had no idea what was the matter. Finally he spoke. “I think it's time I told you where I really come from.”