The Doctor property of the BBC. Firefly of course property of Joss 'the Boss' Whedon.

"And you keep all of this running yourself, you say?" The old man stroked his chin. "Quite impressive for one your age. I'm sorry, what was your name again?"

She grinned. "Kaylee. Kaylee Frye. What's yours?"

"I'm the Doctor."

"Really? We have another doctor on board, maybe you've met him. What are you a doctor of?" She leaned forward, eyes shining.

The Doctor leaned back slightly, and chuckled. "My, you're certainly a cheerful young lady! I'm really more of a generalist, myself. A bit of this, a bit of that... I've found it's all useful in what I do." He paused, then said, "And yes, I have met young Doctor Tam. We had a bit of a... conversation about my medical history. A most focused young man, and a brilliant physician, really."

"And what do you do?"

"Jehoshaphat, aren't you a curious one! I go places, do what I can to help, whatever it is... it's somewhat difficult to explain, I'm afraid."

Kaylee narrowed her eyes at him, but a small half-smile stayed on her face. "So you don't want to tell me right now. Shiny. But you know, you never really did tell me your name!" She started to give him a playful punch in the arm, but checked it quickly. "So what is it?"

He smiled just a smidgen more broadly. "Doctor John Smith, if you like. And starship engineering does happen to be one of the things I've dabbled in. Would you like to compare notes?"

"Would I?!"

--

Mal swung himself into the doorway. "Kaylee, is the engine going to be ready for..." The next words died on his lips.

Both Kaylee and and their elderly passenger sat bolt upright from an open panel and a box of weird parts. Both were spotted with engine grease; the old man seemed to have lost his fancy cape and coat, leaving him in a wine-red vest and a rather frilly shirt.

"What in 十九个燃烧地狱 is going on here?" he snapped.

"I'm terribly sorry, Captain," said the Doctor, standing up. "Your engineering officer is one of the most gifted I've seen in a long time, and I'm afraid I must have badgered her awfully until she would show me how she kept a Firefly-class ship running this long." He sighed. "I apologize. I will return to my quarters."

With that, he was past him and down the hallway.

Mal blinked. "Er..." He was about to continue, but suddenly found himself face-to-face with an extremely irritated Kaylee.

"Why'd you have to be so mean to that nice old man?" she said. "It's always nice to see someone at least trying to keep up with his field! I 'spect you'd like people to respect you when you reach that age!"

She folded her arms and glared at him.

Mal took a step back. Blinked.

Then, his face got back to it's more usual expression, and he took a decisive step forward.

"That's neither here nor there. We need these engines up to snuff for a good hard burn on this run. And you're to clear any strangers pokin' about our engines with me first. We don't want anymore unpleasantness on our long runs, dong ma?"

Kaylee gave him a hard look for a few seconds more before dropping her eyes with a sigh. "Aye, Cap'n," she said, and turned back to adjusting a bolt on the side of the engine.

--

十九个燃烧地狱 - nineteen burning hells

dong ma - do you understand?