Fandom: Doctor Who/Harry Potter crossover

Characters: Ten, Donna, Sirius Black

Warning: This contains a lack of accuracy.

Summary: The Doctor decides to take Donna to wish someone "Happy birthday".

Disclaimer: I own a few of the books, and that's about as far as it goes.

A/N: Originally written for the Big Bang challenge at bbcland as a birthday present for mrsdianablack. Sorry it's late, love; but better late than never.

A Harry Birthday

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"Who did you say we were visiting again?" Donna asked as she held on desperately to the controls of the console. "Because it sounded like you were taking the mick for a second."

The Doctor puffed up indignantly. "I assure you I was not taking the mick, or anything else. I just wanted to catch up with an old acquaintance. I'm sure you can understand such a sentiment."

"Keep your hair on! I wasn't trying to insult you, Spaceman; I was only asking," she tried to placate him, rotating the gyroscopic reel when he indicated for her to do so.

"Good!" He beamed at her. "Seeing as you worked in a library for a while I thought you might appreciate this trip."

"Not more man-eating books! Please tell me we're not meeting the original Moby Dick," she snarled.

"We're not meeting the original Moby Dock," he complied. "But we are meeting an original."

"Really?" she carefully considered him as she tried to guess who. Or should that be guess what? "Is this to do with Stephen Hawking? Shakespeare? Erm… Ooh! I know! You're taking us to visit the vampire that inspired the Twilight books."

"No," he replied slowly. "Vampires don't exist in human form; though Plasmovores could be mistaken for one, I suppose… No, I'm taking us to see a real, live wizard, Donna."

"What? Like Gandalf? I'm going to meet Merlin? THE Merlin?" She almost jumped up and down in her excitement.

He waved his hand about dismissively. "Not him! Now he was made up. I'm taking us to see Harry Potter."

"No!" she exclaimed in disbelief. "Are you serious? Harry Potter! Did you just say Harry Potter?"

"I did!" He bounced happily on the heels of his feet. "I thought we could go and wish him a happy birthday!"

"But his birthday is in July," Donna blurted out. "It isn't July anymore."

"Time machine, Donna," he pointed out, swivelling his finger to encompass the console room.

"Idiot," she readily replied, pointing at him.

"Oi! Don't get personal," he griped.

"Don't get patronising then," she retorted.

They both huffed their indignation before going back to normal. "What do you think?" he asked, tempting her with a quirk of his eyebrow.

"I think 'yes, please!'" she replied, and pressed the materialisation button for him.

They stepped out into an extremely dark bedroom. "Are you sure this is the right place, Doctor?" Donna whispered to him.

"I'm certain," he whispered back. Sensing her disbelief, he added, "Honestly, I am!"

An unknown finger tapping on Donna's shoulder made her shriek for a second. "What are you doing in my house?" the owner of the finger demanded. "And how did you get in here?"

"Hello! I'm the Doctor and this is Donna," the Doctor automatically explained with a cheery smile. "We were looking for Harry Potter."

"Why?" the man asked suspiciously.

"To wish him a very happy birthday, of course!" the Doctor replied, beaming at him smugly.

"He's not here," the man told them.

Donna pushed her way forward to peer at the man intensely. "Here, don't I know you? You look just like… Oh my God! You're Gary Oldman!" she shrieked excitedly.

"No I am not!" the man answered indignantly. "I am Sirius Black."

"No!" both the Doctor and Donna gasped in surprise.

"Lovely to meet you," the Doctor gushed, grasping Sirius' hand firmly and shaking it. "May I say what a fan I am of your… erm… achievements?"

Sirius gave them both a very dark look. "Thank you; now if you could leave my home please…"

"That's not very friendly of you," Donna pointed out. "We're standing here, practically drooling all over your socks because we think you are terrific, and you're chucking us out!"

"Young lady, you may be a fan of mine, but I do not know you and your husband; and if you think I am going to show any muggle that turns up on my doorstep, let alone in my home, where Harry Potter is, then… Why are you two whispering together? What's going on?"

"He didn't, did he?" Donna questioned the Doctor.

"He most certainly did!" the Doctor confirmed.

"Well?" Sirius loudly demanded an explanation.

"Ah! You see…," the Doctor began, scratching nervously on his neck, "Donna and I are… we're not… and you obviously think we are…"

"The thing is, Mr Black," Donna took over the explanation, "we're not a couple, and yet even you can't see that we aren't. Bit disappointing, if you ask me? I mean, if a wizard as famous as you can't see the truth then you need to go back to Hogwarts!"

"Well said, Donna," the Doctor encouraged her, nodding his head. "In fact, Mr Black, we are thoroughly unimpressed; but that's by the by."

"Doctor, isn't it? I must ask you to take your wife," Sirius said, deliberately emphasised the relationship, "out of my home, using whatever magical means that brought you here."

"Magic!" the Doctor snorted with derision. "I use science, Mr Black, and don't you forget it!" He turned his attention to his companion. "Come Donna; obviously Harry isn't here, so we'll have to ask Mr Black to pass on our good wishes."

Donna took his offered arm. "Okay, Spaceman. Do you fancy going to get some cake somewhere else? I can think of a nice little shop just off Covent Garden. "

"Ooh, that would be lovely; and I promise not to do the thing again," the Doctor greeted her suggestion with glee.

"You'd better not," she threatened him. "Or your privileges will be withheld."

"But Donna!" he whined as they walked and reached the TARDIS doors. "How can you be so cruel?"

"Cruel to be kind, mate," she huffed out, just as they disappeared inside and the doors shut.

Sirius watched with interest as a strange elephantine sound filled the room, and the large blue box they had entered dematerialised. "Not magical, indeed!" Sirius murmured, laughing to himself. "That box was not any science I know of. And not married! Who are they kidding? They might as well have it tattooed on their foreheads." Chuckling to himself about his absurd unwanted guests, he set about making the house ready to greet Harry when he arrived later that day.

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