Disclaimer: I do not own Doctor Who or Harry Potter. I'm 100% sure… Actually I'm 99.99% sure. Hold on I gotta check something.

This is inspired by the Bibliomaniac's story called "De-Aged". There will be similarities but overall the story will be different. But really check out the Bibliomaniac's story, it's awesome!

After taking a long break from this story I edited the first five chapters that I already posted. I'm not sure if I will continue or how often I will post if I will. Thank you to all who read it!

Also this is the Eleventh Doctor and set during the first Harry Potter book.

Chapter One - Dear Mr. Smith

The Doctor stood leaning against the console in his TARDIS, an upside down book in one hand, a cup of tea in the other, and a fez balanced precariously on his head. He was alone on the TARDIS for the moment, having dropped off Clara a few days ago. It was quiet and calm for once.

It didn't last long. As always something had to go wrong. Today that something appeared to be an unidentified object crashing right into the TARDIS. The TARDIS wobbled at the collision and sent both her and the object off course. The Doctor stumbled dropped his book, spilled his tea all over the console, and somehow managed to keep the fez on his head before falling down and struggling to get up. Sparks flew from the places the hot drink had spilled and the cup, which the Doctor had dropped a second ago, shattered. The TARDIS righted herself with a second jerk, causing the Doctor to, once again, fall straight down.

Sparks continued flying from the console. Apparently the liquid had spilled over something important. The Doctor reached for his sonic screwdriver and pointed it at the console. It seemed to have worked for a moment before another spark shot off and a jolt of energy hit the Doctor. It wasn't painful and through the comotion the Doctor barely noticed it.

He soniced the console again and all the sparks died down. The Doctor let out a breath and his face split into a smile.

"Now that is much better than a book!" He exclaimed. "Now let's see what it was that hit us." He grabbed the screen and turned it toward himself. The screen showed the object and it's trajectory. It was heading straight toward Earth.

"Oh no, not again! I just hope it's not nanogenes again." He stopped for a moment remembering his time in the 1940's with Jack and Rose. He shook himself out of it. No time to reminisce.

He grabbed the TARDIS controls and followed the object. Thankfully the TARDIS was much faster than it so he caught up to it just before it hit Earth's atmosphere.

Unfortunately at that moment it decided to split into two parts. One half hurtled down to Earth and the other sped toward the TARDIS. It landed with a loud clang in the floor. Whipping out his sonic screwdriver the Doctor scanned it again and then hesitantly picked it up. Nothing happened.

Well, nothing happened for a few minutes. Then something happened.

The half sphere started to open a tiny bit from the center and a bright light spilled out. Suddenly it pulsed forward from the object and for a second everything was enveloped in light. Then it stopped and the light disappeared.

The Doctor fell to the ground. The light had done something to him but right now he could not tell what. Darkness descended over him and he didn't even realize the TARDIS had landed somewhere.

The Doctor awoke feeling as though he had just regenerated several times. It took a moment for him to remember why he lying on the floor with his cheek pressed against the metal grating. He pulled himself up with great effort. His whole body felt tired and he had a bad headache.

Being the Doctor the first wrong thing that occurred to him was that his fez was too big. He then realized that, in fact all his clothes had enlarged. It took another moment before he realized that his clothes hadn't gotten bigger; he had gotten smaller. In fact he was tiny!

"No!" His voice was high pitched. "No!"

He was a child. A child, again! And by the looks of it he was around 11 years old. The Doctor groaned and fell back down to the floor. He did not want to relive his childhood. If he was right, and he usually was, then he would begin to revert to his childhood behaviors and habits. He had always been a bit of a weird child. He was extremely curious and often didn't think things through or consider the consequences. He loved running around and exploring. However he would also love reading and learning. As a child some days he could barely keep still while others he would sit alone for hours on end. Some things didn't change, like his morals or his aversion of violence.

He had though always had a bad habit of blurting things out at the most inopportune moments. Of course it was this same skill that helped him escape many sticky situations, or cause them to happen in the first place.

The Doctor tried to stand again but found himself back on the floor after tripping over his ridiculously large clothes.

"Right, first things first, I need to get some clothes." He muttered to himself as he made his way towards the closet where he knew he had some kids clothes. After some deliberation he decided on an outfit that consisted of a white button down shirt with a sweater over it, faded blue jeans, and red converses and bowtie. He had been unable to find a smaller version of his fez to great disappointment, so he decided to keep the one he had even if it was too big.

Now that he was no longer tripping over his clothes at every step came the problem of how to turn himself back into an adult. Unfortunately, he had no idea what the object was or how to fix it. He could barely reach the controls as he was quite small for his age. Finally he pulled the right lever and the TARDIS started moving. Then with a loud crash she settled back down.

"What?" The Doctor asked, completely baffled. He pulled the lever again and pressed a few buttons. The TARDIS disappeared and with another jolt reappeared in the same place again. The Doctor pulled out his sonic and scanned the panel.

"Oh, come on! We're stuck here! It's like we're in a bubble, unable to leave. I'd say we could go, uh," He glanced back down at his screwdriver. "About as far as Scotland. Hey Amy…" He trailed off remembering his companions were no longer here. For a moment he stayed like that and you could truly see his age. Then he smiled again and it was gone.

"Now, where would an eleven year old kid blend in? Somewhere fun, with adventure and danger." He mumbled to himself.

The TARDIS chimed happily and decided to take matters into her own hands. She lit up and quickly spit out an envelope that the Doctor grabbed. Taking it he realized the envelope was made of a thick parchment and addressed to him:

Mr. J. Smith

The console room

The TARDIS

London

He opened the envelope and took out the three papers inside. The first one read:

HOGWARTS SCHOOL
of WITCHCRAFT and WIZARDRY

Headmaster: Albus Dumbledore

(Order of Merlin, First Class, Grand Sorc., Chf. Warlock,

Supreme Mugwump, International Confed. Of Wizards)

Dear Mr. Smith,

We are pleased to inform you that you have been accepted at Hogwarts School Of Witchcraft and Wizardry. Please find enclosed a list of all necessary books and equipment. Term begins on September 1. We await your owl by no later than July 31.

Yours sincerely,

Minerva McGonagall,

Deputy Headmistress

"Brilliant!" He said once he had read through the letter. Of course he knew of the magical world, he had even helped a few times, but he had never learned magic. This was also fairly convenient, as it would provide him with a place to live for a few months, until he could figure out how to turn himself back. He looked up at the TARDIS and she gave a smug ding.

"Yes, yes, you're very clever. I suppose it is a good cover. I can stay there while I figure out how to fix this."

He pulled out the second sheet of paper which had all the required items on it. The last sheet was the one he had to send back to confirm that he would be attending. The Doctor filled it out quickly and stuffed it into his pocket. He would have to figure out how to send it later. Despite being in this situation he was feeling rather excited. He never could resist a challenge.

He stuck his head outside the TARDIS and noted that the Leaky Cauldron, the way to get into Diagon Alley, was just across the street from where the TARDIS had parked.

"It's almost like you planned this." He muttered. From behind him he could hear the TARDIS make an offended noise.

He glanced down at the second sheet of paper again and then hurried off into on of the many storage rooms where he knew he had a trunk, one that was bigger on the inside, of course. After making his way through some old gadgets and artifacts he found what he was looking for. It was covered in dust but would still work wonderfully. He removed the false bottom and clambered inside to make sure everything was in order there. Apart from some dust and cobwebs it seemed to be just as he left it. The Doctor sighed, he would clean all this later, and climbed out of the trunk again.

The TARDIS showed that it was July 29th today, he had time until school started. He decided that he would stay at the Leaky Cauldron until term started since it would draw too much attention if a kid was constantly walking in and out of a police box, despite the perception filter. In fact the Leaky Cauldron too had a perception filter, though a weaker one. He assumed that this was to keep muggles out, though he really didn't see the purpose of that. The way to Diagon Alley was still concealed even without the pub being hidden.

This was the problem with wizards. They really opposed change and instead prefered to stay secluded and not change at all.

The Doctor made his way into the bank room of the TARDIS. He didn't usually carry money with him but he did have it. In fact he had a lot of it actually. He didn't really remember where it all came from to be honest.

He opened the door and made his way to the section that contained the wizarding money. Pulling out a money bag he grabbed several handfuls of galleons, sickles, and knuts, and shoved them into the bag. That should last him for a year.

The Doctor made his way back to the trunk, grabbed it and, carrying it behind him, crossed the street and entered the dingy pub. As he walked in the people inside ceased their conversations for a moment and turned to look at him. There was a moment of silence. Then, everyone turned back and the conversations resumed. He walked up to the innkeeper.

"Hello." He said. "I'd like to book a room until September 1st."

"Ah! Hogwarts student are you?"

The Doctor nodded.
"Well, are your parents around?"

"No sir. I'm by myself."

Thankfully he didn't seem to be too surprised at that. The innkeeper led the Doctor up some stairs and into a room with a bed and a small desk. He sat down on the bed and contemplated what had happened to him recently. He looked out the window; it was getting dark. Perhaps he would visit Diagon Alley in the morning.

The Doctor stood at the entrance to Diagon Alley. It was magnificent! He had been to many different markets and fairs on various planets but this was different. Perhaps it was because he was a child and therefore had the emotions of one, but he was totally in awe, frozen for a few seconds.

Then the moment passed and the Doctor closed his mouth and entered the magical world. There were shops for books, robes, and even brooms. He had to restrain himself as he wanted to go everywhere at once. The Doctor took out his list again and scanned it. Cauldron, scales, telescope, various potion items (at this he frowned, it would make much more sense to just use chemicals, rather than specific items. He would have to get some of that too.), robes, wand, and books. He would leave the books for last, as he was likely to stay and read until the shop closed if he went there first.

The first thing he did was go and send off the form he had filled out. He did not want to forget. Then he went to buy the items required for potions. The shop smelled terrible but there were so many things that interested him. Potions was just a slightly different version of chemistry, something that he had always found fun. It had been hard, however to convince the storekeeper to let him buy some of the more dangerous chemicals, but he had managed it at the end.

He then went to buy robes at "Madam Malkin's Robes for All Occasions", where the witch working there fitted him with robes, though with much trouble. The Doctor simply couldn't stay still for more than a minute today, which made it rather hard for her. He didn't really like the robes all that much, it didn't fit his style, but as they were a necessity he got them.

He already had a cauldron, telescope, scales, and both glass and crystal phials, but the list required a standard set, so he had to get all of it again. He then trudged off to get a wand. The wand shop was small and dimly lit and cluttered with boxes. The shelves were practically bursting with them. At first the Doctor didn't see the old man, as he was still looking around, so when he spoke it caught him off guard.

"Good afternoon." A soft voice spoke.

The Doctor turned in surprise and saw the owner of the voice. This must be Mr. Ollivander. "Hello." He said. "I've come to get my wand."

"Oh, yes, very good, very good. What is your name?"

"The Do— John Smith." He caught himself.

"And, Mr. Smith, Which is your wand hand?"

"Ambidextrous." He said. "Though I suppose preferred right."

"Hold out you arm then, thank you."

He did so and a moment later he was being measured every which way. While that was happening Mr. Ollivander was rummaging around the shelves. Finally he pulled out one box and brought it over to where the Doctor stood.

"Try this, beech wood and unicorn hair, nine and three quarters inches, quite flexible."

He handed the Doctor the wand. It lay in his hand completely still and he could feel it's distance. It almost seemed to dislike him.

"Well, give it a try."

He lifted his hand and immediately a glass vase shattered.

"Sorry." He said quickly.

"No matter. No, no. That wont do at all." He muttered, taking the wand from his hand and going off to find another wand.

"Cypress and dragon heartstring, eight and a quarter inches, springy!" He handed the Doctor another wand. This one seemed to be a bit annoyed at him. He waved it and accidentally sent all the papers on the desk flying.

"No, no. it must be something else." Mr. Ollivander muttered again and strode off to get a new wand for him. "This one, maple and dragon heartstring, twelve inches, stiff."

He had barely touched this wand when it jumped back from his hand and onto the floor. Mr. Ollivander continued as if nothing had happened.

"Here! Pear wood and phoenix feather, nine inches and a half, slightly springy." he said, handing the Doctor the wand.

As soon as the wand was in his hand it exploded. Shaking his head and muttering something under his breath Mr. Ollivander retreated further into the store. He pulled out wand after wand, and after they barely touched his palm snatched it away. Finally he returned with a dusty box.

"I've had this one for ages, in fact my grandfather said it had been given to him by an old friend. I wonder if…" He took out the wand. "Maple and phoenix feather, eleven inches, very flexible. Perfect for travelers and explorers. This wand can not stay in one place too long or it will grow heavy and lackluster. My grandfather told me this was the wand of a great traveler. The stories he used to tell..." He trailed off and handed the wand to the Doctor. When his hand grasped the wand a peculiar feeling engulfed him, a warmth streaming from the wand. He lifted it and pointed and a few sparks came out of the end. He examined the wand and at the bottom he could see a small carving. When he examined it further he saw that the carving was Gallifreyan. "The Doctor" was carved into the handle. He wondered how this wand had gotten here; who had given it to Mr. Ollivanders grandfather? The only person who could have written this would be himself. He would have to figure this out later.

"Yes, that seems right. That will be seven galleons." Mr. Ollivander said, shaking the Doctor out of his thoughts. He handed over the money, took the wand, and left the shop.

His next stop would be to get books. He was rather excited for this one as he loved to read, so he quickly made his way into "Flourish and Blotts" the bookstore, and quickly found all the required books as well as several of his own choosing. In fact he had picked up several books for later years as well. When he had paid for all his purchases he sat down in the bookshop, opened a book and began to read. He had finished three and a half books by the time the store began to close. When the owner had kicked him out the Doctor returned to his room in The Leaky Cauldron and continued reading.

He wanted to learn as much as he could about the world and the time period. Though he knew of the magical world he had never been a part of it. He was especially intrigued to how magic actually worked. He knew that wizards drew on psionic energy and he supposed that the wands helped harness the energy and concentrate it. He wondered if doing magic without a wand was possible. It must be, but it probably required much more concentration and effort. He understood the theory but wasn't able to actually try it. That would have to wait until he was at school.

The next weeks flew by. He visited Diagon Alley a few more times, to replenish his supply on books and to see what other things were sold, but he spent most of his time reading. He had also cleaned out the trunk and had found that it would be an adequate alternative to the TARDIS while he was at school. He had also decided that he would send the TARDIS off to stand somewhere on the outskirts of the castle, so that it wouldn't draw attention, but if need be he could access it.

On the morning of September 1st he awoke early in the morning and looked around his room. He still had to get all his books into the trunk, something he had neglected doing for the last week. Grumbling and rubbing his eyes he got up, dressed, and then proceed to clean up his room, by haphazardly throwing everything into the trunk. He had noticed that since he aged himself down some of his habits and traits that he had as a child had also returned. That included his distaste for cleaning.

He gathered his things, shoved them into the trunk and carried it downstairs. Then he walked to the TARDIS, took the last things he thought he might need and sent her off to wait at Hogwarts. His next stop was platform nine and three quarters.

A/N: So as you can see I changed some things and kept some things. I'm not sure exactly sure where I'm headed with this story but I have a better idea than before. I hope you liked the improvements.