A/N: Half of this conversation happened in my strange little mind when I was in the shower this morning. At that point, it was going to go in my behemoth of a DW story, The Year That Never Should Have Been, lovingly shortened to TYTNSHB, or, as I've always called it, Torture. However, twelve hours later when I've finally sat down at my computer, it's got a whole different direction, setting, overlap and secondary character. *Grin* I've always wanted to write Donna Noble.

Why and why not

"Why did you love her?"

The Doctor blinked in surprise, drawing his concentration away from the garish Xeraboan landscape that was flying past. "Sorry?"

They were on a long distance hovertrain journey along the equator of Xerabo, the purpose of which being to get back to the TARDIS. The Xerabs hadn't quite grasped the idea that their teleport system would be so drastically painful for a human. Nor that Donna's resultant screams would be so drastically painful for their own eardrums.

After sorting out the consequent diplomatic incident, repairing the hearing of a few aliens with the trusty sonic screwdriver and of course putting all Donna's internal organs back together after leaving her safely in stasis for a bit (she hadn't yet forgiven him for leaving her there for six whole hours), the dynamic duo had been shoved on the slightly outdated hovertrain for a journey that would have taken ten minutes on any civilised world, but here would take ten hours.

Of course, on Earth it would have taken days. The Doctor's definition of 'civilised' was somewhat different to Donna's.

Four hours in and Donna was lying listlessly on a bunk, staring at the ceiling while the Doctor sat with his trainer-clad feet resting irreverently on the plastic table that seemed to be a vital feature on trains. The conversation had traversed the murky subject of Donna's forced homeostasis, of ways the Doctor could make it up to her, of exactly how he expected humans to explain away all the aliens they'd seen invade (and the several that she'd missed), and had drifted gently into a rare silence.

Until now.

"Why did you love her?" Donna repeated, shifting so she could stare searchingly at him.

"What? Who?"

Donna rolled her eyes. "Rose, you idiot. Why her?"

The Doctor boggled. "What in the universe do you mean: 'why her'?"

Inwardly, Donna made a mental note to avoid the word 'love'. Evidently, she would get much further without it.

Outwardly, she pressed on: "I mean you're an alien, she's a human, you're nine hundred, she's—what, twenty?—you're a complete idiot when it comes to seeing people care for you, she's... well, I don't know, I s'pose she might be exactly the same, but—"

"Donna, I'm the last of my kind," he reiterated. It never got easier to say. "There is no one in the universe like me."

"Yeah, which means that you can't exactly limit yourself to your own species. So why her? No, scrap that, why humans? You keep going on about how we're idiots and all that."

"You're genius idiots, though," he reminded her. "Obviously you're not as clever as me—"

"Obviously," Donna muttered.

"—but you've got so much that Time Lords never had. Look at you, asking me to save someone, anyone, from the ruins of Pompeii! And me, with all my Time Lord righteousness, about to leave them all behind..."

Donna sat up. "Yeah, but you thought you were doing the right thing," she argued.

He, too, took his feet off the table and leant into the conversation. "But I was wrong," he stated. "I know so much more than you, but I was still wrong, and you were right. That's what's brilliant about humans."

She took a moment to absorb this.

"Still doesn't explain why her," she persisted, stubbornly.

He threw his head back. "Why does it matter?" he asked in despair.

Donna shrugged. "It doesn't. Doesn't stop me asking."

How was it even possible that she could outsmart him by admitting she had no answer?

"Cos the way I see it," she continued, "you could have had your pick of the universe. Well, almost. I swear, even that Zerob queen one—"

"Xerab king."

"Yeah, her, him, whatever, was all over you! And you said Martha fancied you, and she's a lovely girl; she's brave and strong and clever to boot."

"There's different types of clever," the Doctor reflected.

Donna grimaced. She still wasn't getting anywhere, so she tried a new tactic: "Tell me about her."

"Who? Martha?"

"No, you twit! Rose!"

He sighed, and put his feet back on the table. "Rose Marion Tyler. Lived on a London council estate, worked in Henrik's, lived with her mum, Jackie; her dad died when she was a baby. She had no A levels, only a handful of GCSEs, including a D in Science and an A in English Language, she lived with an abusive boyfriend for six months when she was sixteen before he dumped her, and she'd only cleared the last of the debt he left her with two months before I blew up her job."

It wasn't the prettiest of pictures. Donna was about to say something to this effect, but then he spoke again.

"When I told her to go home and forget me, she looked me up. When I took her home twelve months too late, completely by accident, she never blamed me for the murder charges against her boyfriend. When we were trapped in 10 Downing Street, and I had to choose between the world and her, just days after I met her, I hesitated. When she saw that, she told me to choose the world.

"When I sent her home from a space station two hundred millennia in the future to save her life, she ripped the TARDIS open to come back to me. She pulled the entire time vortex inside her head. She became a goddess. She had power over everything: life, death, time. She was time. And she said to me that she wanted me safe. She destroyed my enemies and saved my life. And when that was going to cost her hers, I died for her.

"Oh, but Donna... I travel through time. Even in my title, I pretend to have mastery over time. I pretend that time is mine, but the only truth in the history of everything, ever, is that time rules over us."

"How could I not love her?"

A/N: So, now I turn over to you. Any requests for oneshots that could feasibly be 999 words in length? In case you hadn't guessed, I'm a bit of a Ten/Rose shipper, so that's a constraint, as is that it has to pertain to Ten. Other than that, fire away!