Disclaimer, I'm not overly familiar with this Doctor or companion.
The Doctor made his way into the control room, his companion following behind.
"Now then Ace," he stopped at the consel, turning. "Where do you want to go? Perhaps the lava-falls of Enlison 12? We can roast marshmallows. Orr, we can go visit Mars in the 23rd century. Or we could-"
The Doctor stopped, and he and Ace turned to the TARDIS doors, to the sound of scratching. This was most confusing because they were currently on the moon! The Doctor and Ace hurried to the screen. The Doctor flicked a switch, and they saw, to their ever growing confusion, an owl.
"What's an owl doing here, professor?" asked Ace.
"I don't know," answered the Doctor, thoughtfully. "But I have an idea. That's not any ordinary owl."
The Doctor started pressing buttons. "You can't see it, I imagine, but that bird out there is surrounded by magical energies." As he finished talking, the screen shifted, and Ace could see strange colourful ribbons of energy around the bird.
"What do you mean, magic? And what are those colours, professor?" she asked.
The Doctor frowned. "I suppose magic is the wrong word, although it's the easiest word. I mean the use of hidden psychic energies and abilities by humans, and some non-humans, to manipulate the reality around them. To an extant. There's a hidden society on earth that are born with ability to tap into the otherwise untapped psychic potential. They channel it through a conduit, a wand, and use it to shape the universe. Very localised. Those colours are the effect of what you would call a spell."
Ace took a moment to let this sink in. "So, why is there an owl?"
The Doctor spun up. "Well, it's a messenger owl. It's brought me a message." He strode over to the doors, and swung them open. "Hello! Come in. There we go."
The owl flew in, and perched itself on the Doctors shoulder. It had an envelope in its beak, which the Doctor took. The bird flew out then, in a flurry of feathers. The Doctor opened the letter, and his eyebrows rose in surprise.
"What is it, professor?" inquired Ace.
"An invitation," said the Doctor, holding up the letter. On it was writing, and a strange crest of arms that Ace didn't recognise.
"School!" piped the short Time Lord.
"Shool?" repeated Ace.
"Yes, Hogwarts School of Witchcraft and Wizardry," explained the Doctor, returning to reading it. "1991." He frowned. "I know that year, don't I?" He moved and placed the letter on the TARDIS console, and placed his hand on his chin in thought. "Yes, that's the beginning of the Second Wizarding War in Britain, isn't it?"
"What are you going to do?" wondered Ace.
"Well, I'll accept," answered the Doctor, moving about suddenly, flipping switches, pressing buttons, all in a familiar pattern.
The TARDIS whirred, and stopped.
"Where are we, professor?" asked Ace.
"A train station, 1999," answered the Doctor. "One year after the war has ended. I'm waiting for you here, Ace."
"You are what they call 'muggles'," explained the Doctor with distaste. "You can't use magic, so you won't be able to join me in Hogwarts. So I've skipped ahead to the end of it. I've graduated and the war is over." He opened the doors, to see himself, waiting outside.
"Ah, hello Doctor," said the other Doctor, who was wearing robes with question marks all over them.
"Ah, hello Doctor," said the Doctor. "Is that what I have to wear?"
"Yes, I'm afraid so," lamented the Doctor. The Doctor cringed.
"Oh well, goodbye Ace," said the Doctor. "See you later."
"Bye, professor, have fun," waved Ace. "Hello Doctor."
"Hello Ace," said the robed Doctor.
The Doctor then closed the doors, and went back to the console. He set the coordinates, and a few moments later found himself in an alleyway. He went into a room, and took out a number of bronze, silver, and golden coins, which were the resident currency. Exiting the TARDIS, he searched around for a shop.
"Now then, what do I need first?" he muttered to himself. "A wand, probably. Now where shall I find one? Ah, that'll do." He walked over to a shop with golden letters on the front, swinging his umbrella.
The bell rung, and the Doctor walked in. He tipped his hat.
"Hello. Ollivander, I presume," he called to the man at the desk. Ollivander, if he had to guess.
"Ah, hello. Correct," said the man, looking up.
"I'm in need of a wand," said the Doctor. "I'm afraid I don't remember the specifics of my last wand."
"Not a problem," said Ollivander, getting out a few equipments. "What's your name, and which hand?"
"I'm the Doctor. Ambidextrous, but I use my right hand the most," answered the Doctor.
A few moments and measurements later, and Ollivander had found a wand.
"12 inch, heartwood, dragon heartstring," he explained, offering the wand. The Doctor took hold of it, but it felt rather uninviting. The Doctor put it back.
"No, it doesn't feel right," he commented.
"Yes, I agree," agreed Ollivander. He went and placed it back, getting another wand. "Beech wood, 9 inch, phoenix feather core."
The Doctor moved to take it, but almost immediately felt against it. "No, not this one either, I'm afraid."
Ollivander took it back. This went on for a few more minutes, until finally Ollivander brought out an experimental wand.
"This wand is rather experimental," he began. "I've had it for a while now. It's made of a variety of woods; yew, walnut, sycamore, silver lime, redwood, pine and pear, um, maple, holly, some hawthorn, a bit of fir, a few splinters of elder, dogwood, a deal of cedar, cherry, and beech. It is the most woods I have ever managed to fit into a wand. It has phoenix feather, dragon heartstring, and unicorn hair. It's 12 inches, and quite bendy. I have my doubts, but I feel this one might be the one."
The Doctor stretched his hand out to it, and found it... inviting. He took hold of it, and gave it a swish. It produced a light, which swam around him, before disappearing.
"Ah, I believe this is the one," said the Doctor.
"Yes, yes I think so," said Ollivander. "You shall be an incredible wizard, Doctor, very incredible indeed." He then stretched out his hand. "That'll be fifteen galleons."
The Doctor sighed. "You don't have much of a sense of occasion, do you? Oh well." He reached into his pocket and pulled out a handful of coins. "Here you are. Thank you." He tipped his hat, and left, putting the wand in his inner pocket.
A while later, and he bought an owl and a few dozen books on a variety of magical topics, including ones he won't need for another few years. He suspected he would need some reading material. He went to his TARDIS, and set coordinates for platform 9 3/4. He materialised on the station, barely noticed by the passer-bys. There was a train already waiting. He put everything, save the owl, in a small suitcase, including some none magical ones, and quickly found himself a robe that the TARDIS made, littered with question marks, and filled with a few jelly babies. He exited the TARDIS, and bid his farewell.
"Goodbye, old girl," he said. "Don't worry. It's only for a little while. I'll come and visit you when I can." With that, he turned and boarded the train.