Author's Note: This is an idea I've had on my mind for a long while. Of course, how could anyone not take advantage of the fact that David Tennant plays both characters?

While the characters of Harry Potter look like their movie counterparts in appearance, plotlines and character personalities are based on the books. This story takes place towards at the end of The Goblet of Fire, during the chapter "The Parting of the Ways."

For Doctor Who, this takes place in Season 4 a little after "The Unicorn and the Wasp."

Disclaimer: All rights belong to their respective creators.

Everything had been carried out as told. The Triwizard Tournament had been manipulated. Harry Potter had been named the fourth champion. Each task was twisted to suit the boy's favor. And it was Potter's blood that ultimately revived Lord Voldemort at the end of the night. The deed was done.

And it was all thanks to his most faithful servant.

But it seemed as though Barty Crouch Jr.'s metal lapse at the very end was finally going to cost him. In his eagerness to intercept Potter, Barty had compromised his position in posing as ex-Auror Alastor "Mad-Eye" Moody for an entire year via Polyjuice Potion.

There stood Minerva McGonagall, Severus Snape, and Minister of Magic Cornelius Fudge—the former two looking down upon him in contempt; the latter in utter fear. Of course it was this unfortunate fear of a flustered Fudge that resulted in a dementor being brought along to accompany him to the Defense Against the Dark Arts office.

The dementor was chillingly close to Barty now and there seemed no time left to believe that it would be stopped. Not even Minerva McGonagall or Severus Snape, who were both taken aback by the foul beast's sudden unwelcome appearance, were prepared as one of the scabbed, decaying hands gripped tight around Barty's throat, and drew a great, deep rattling breath. The raised voices of both Professors trying to ward off the dementor while simultaneously telling off the Minister of Magic for this most detestable display of cowardice gradually fizzled out into woolly ringing in Barty's ears.

He felt the frozen wasteland that lay who knows where as all of his worst memories and nightmares wove in and out in fuzzy patches of haze around his head—trying to garner the attention of his father to no avail; being imprisoned under the Imperius Curse for over a decade; the sham trial with him begging and pleading his innocence, where noone believed him but his dear mother; the fateful night in question and a flash of green light as screams of unholy terror pierced his ears….

But the dementor was just getting a mere taste of its prey and unhinged its mouth even wider.

Everything was spinning. He was getting dizzier and dizzier by the second. The last thing Barty remembered seeing was the foul beast's decaying, blackened rotten mouth before he succumbed to the unwelcoming darkness that engulfed his very consciousness.

No witch or wizard in history knew what would happen to the soul once a Dementor Kissed its victim. Being as it was, Barty was quite surprised to find himself slowly regaining consciousness. His limbs were slow to catch up to his mind as a muffled sound reverberated against his ears. He felt cold. His body trembled, and it came as an even greater surprise to Barty that he still retained one.

'What?' was the very first thought to cross his mind as the muted buzzing noise began to clear—it was a voice calling out, banging against his eardrums.

"Doctor? Doctor! Are you okay?" an abrasive, female voice shouted as it closed in on him.

Finally getting the feeling back within his body, Barty slowly flexed his fingers before sensing some sort of burning light hitting against his eyelids. It felt like flames were tickling him, as though melting away the iciness that racked his body stiff. He groaned in response to the concerned voice.

Everything felt sore and alien to him.

"Oi! Don't you go dying on me, Spaceman! Doctor, wake up!"

Barty finally coaxed his eyelids open and he clumsily shielded himself from the intense white lights shining around him. He groaned again, wondering curiously how he was welcomed by the warmth of light as opposed to the unholy, glacial crevasse of darkness that the dementor was supposed to have sucked him into.

"You're finally awake? Good. Then quit messing around and get your skinny space arse up already!" exclaimed the caustic voice, which Barty now saw came from a redheaded woman standing right above his head.

At first, he believed her to be a Weasley, as she went on, "What in the world happened to you? Did some sort of Martian sickness come over you or something?"

His eyes still adjusting to the sudden light, Barty pushed himself into a sitting position and shook his head, trying to dispel the dizziness that still racked it. Once the dark patches of spots faded away from his vision, he was befuddled to find that not only were McGonagall, Snape, and Fudge nowhere to be found, but that he was no longer in the Defense Against the Dark Arts office as a whole.

A far cry from where he last found himself in, this coral-esque room was encompassed by round panels of strange lighting and multiple branches sticking out from the floor; to his left was a small ramp that bridged the gap to the door that must've led outside, and right behind him seemed to be a hallway leading to who knows where. Right in front of him stood some grand control console with many buttons, switches, and levers that rose right up into the ceiling and was located right in the center of the obscure room; below was a grating that decorated the length of the floor.

To say that Barty was speechless was a vast understatement. He stared around with his mouth agape, completely gobsmacked.

Unless Hogwarts had some sort of hidden room he hadn't known before, was this some sort of place where the victims who received the Dementor's Kiss ended up? Had this Weasley woman been subjected to the same fate as him? And how did he manage to have a change of clothes, he wondered as he felt the blue pinstripe suit, long brown trench coat, and noticed the scuffed red trainers upon his feet. They fit him just right, a far cry from what he'd worn when disguised as Mad-Eye Moody.

"Oi! Spaceman, didn't you hear me?" asked the ginger woman. Barty, who was still thumbing the fabric of his unfamiliar clothing, looked up at her. She appeared highly distressed. "Have you gone deaf or something? What the hell happened to you?"

"Er…." began Barty. He paused for a second to run his tongue over his teeth. They felt quite odd, although he sounded exactly as he always had when he spoke. "Sorry…who are you? And why are you calling me, 'Spaceman'?"

Barty thought the redhead's eyes were going to pop out of her sockets as it was her turn to stare at him, mouth agape.

"What do you mean, Doctor? It's me—Donna," she sounded a little hurt as she knelt down next to him. "Donna Noble. Don't you remember?"

"Er…did you just call me 'Doctor'?" Barty asked, totally confused. Wasn't a doctor some sort of Muggle Healer that cut people open? He didn't quite understand why this Donna person, who may not have been a Weasley after all, mistook him for one.

Donna's jaw dropped even further at his words, making her look something akin to a troubled goldfish. She stared at him for a moment before gasping, the gears inside her head seemingly working to draw out a logical conclusion.

"Oh no….you've got amnesia," she finally said, sounding even more worried than before. "Is that even possible for Time Lords? Oh, what am I saying, I'm seeing the result right in front of me! How do I fix this? Otherwise I'm going to be lost in space with an amnesiac alien! Oh, I did not sign up for this!" she finished in exasperation as she stood up and swept around the console, trying to calm herself down.

Though Donna seemed to be greatly unnerved, a lot of words floated right over Barty's head, with 'Time Lord' and 'alien' losing him completely. What got him even more lost was when this Donna person finished her pacing around the console and began speaking to him slowly, as though he were a child.

"Okay…listen. I. Am. Donna," she pointed at herself. "You," she now pointed at him, "Are. The. Doc-tor. A. Comp-letely. Mad. Alien. From. Out-er. Space," she finished, gesturing her arms wide as though she were emphasizing that the entire universe was just outside the door at the other end of the ramp.

Barty furrowed his eyebrows. Had this lady completely lost it? What in the world about him screamed alien? He liked to think he looked perfectly normal, thank you very much. Well, as normal as one who had spent time the entire school year being under the effects of Polyjuice Potion would look. He began to wonder if any of Moody's scars left him looking pockmarked and his fingers grazed the side of his face in slight worry.

"Alien? What do you mean 'alien'?" he asked.

"'Alien' as in you are the barmy skinny streak of a nothing alien around here," Donna supplied in what she believed to be a helpful tone, yet she also sounded exasperated, as though she were explaining something as obvious as one plus one equals two. "Or did your amnesia make you forget about that, too?"

Okay. Now Barty knew that Donna was completely mental.

Though he had no idea where he was and how he had gotten there, he had a half a mind to Disapparate away from this mad ginger lady. Whether he was in some sort of twisted version of dementor hell or not, he certainly didn't want to sit around here all day. Especially not when Voldemort had finally risen again and was probably expecting to see his most faithful servant return back to him.

He patted down his pockets in search of his wand, but froze immediately when he reached within the right breast pocket of the blue suit jacket. He felt something odd. Something pounding inside his chest that shouldn't have been located in that area.

Bum-bum-bum-bum.

Perplexed, Barty moved his hand over to the left side of his chest and felt a similar twin sensation drumming against it.

Bum-bum-bum-bum.

Eyes growing wide in apprehension, Barty placed his hands against either side of his chest, in which the beats thrummed together, as though in complete harmony.

Bum-bum-bum-bum. Bum-bum-bum-bum.

Barty's worry escalated to a shock of horror as he looked up at Donna, who was staring at him as though he were an alien from another planet. Barty swallowed thickly, the fact of that statement perhaps being true slowly dawning upon him.

"Hearts! I've got two hearts!"

"Of course you do! You're not human, remember?" Donna stated impatiently.

"Not human?" Barty repeated, becoming anxious.

He shot up, scrambling around in search of some sort of mirror. There was no way this could be true. There was no way he was some freaky otherworldly being. He was a human. Moreover he was a human wizard. A pure-blood human wizard. There was just no way.

When Barty finally found a reflective bit of rectangular metal upon the console that acted as a mirror, he was prepared for the worst. He was even ready to scream in terror for what he expected to see—some sort of funny little green Martian creature with antennas—when instead he floundered, becoming completely bemused by what greeted him.

"What?" he couldn't help but blurt out.

He looked exactly the same as far as he could tell—same brown eyes, same brown hair, freckles; He raised his hands up to inspect them closely and saw that they didn't appear otherworldly with some sort of greenish hue to them, they remained the same as they ever were. In fact, besides the double hearts and sideburns Barty was definitely sure he did not have before as he felt them curiously, nothing seemed greatly amiss. Well, other than his hair, which was styled with liberal amounts of gel, making it look as though he had a run-in with a bolt of lightning. But besides that, everything seemed completely normal. That is until Barty felt a sudden force hit against the back of his head and he fell back with a groan.

Closing his eyes and shaking his head, Barty was taken aback when a flood of memories that were clearly not his own hit him like a hurricane. Memories of some sort of person called 'the Doctor' began to fill his mind, threatening to burst against his skull.

It was too much for him—this torrent of vast knowledge of the universe mixed with pain and loss ...so much loss…..Faces passed through his mind, many faces of friends lost by his own hand (or was it the Doctor's?) indirectly or otherwise—when he steeled himself against the unwanted waves and drove them off with his skills as an Occlumens. But the damage had already been done.

Barty, who found his hands clutching at his head, his fingers lacing through his thick brown hair as though holding onto it would have saved him from the rushing current of the oncoming storm that had suddenly struck him, now knew he hadn't received the Dementor's Kiss. That this woman was no Weasley or even a torturous apparition of the dementor created to annoy him for the rest of eternity.

No, not in the slightest.

He slowly lowered his hands as he sat up again, this time his head as clear as ever. He gazed around the central console room, soaking in every inch of the alien ship, as Donna ranted.

"Oh, this is hopeless! Of course this had to happen to me! My best mate who just so happens to be an alien completely loses his mind and now he doesn't know who he is, let alone what he even is! I am not saying mum was right, but—"

"Donna, now don't go talking my ears off about regretting coming along with me," Barty grinned in a very Doctor-esque manner, belying the wickedness of his thoughts as he began to think of how to take advantage of this situation.