"Thank you for the key."
"What?" The Doctor looked up from the Tardis console. Donna held up the key to the Tardis that he had given her earlier, while the world was choking. "Ah, yes. I should have given you one a long time ago."
Donna looped the key onto a chain, and put it around her neck. "Did you know, the first few nights on the Tardis - I slept with my clothes on."
"I did, actually," he replied, without looking at her.
"Okay, I won't ask how you knew. But d'you know why?" She watched him closely.
He paused, considering. "No..."
"I wanted to be ready for anything, at a moment's notice. I didn't want you to have to wait while I got dressed, and be sorry you had brought me along."
He laughed. "Guess you got over that, then."
She laughed too. "Yeah, I did. I couldn't sleep! I figured sleep deprivation was worse than taking five minutes to get dressed."
"Five minutes? That'll be the day."
"Oy! Watch it, spaceman."
He continued fiddling with the console, pulling levers, pushing buttons. Then, softly, "I thought you slept fully dressed because you were afraid of me..."
"Afraid of what?"
"That I'd try to... you know...steal your virtue or something."
"Steal my...oh!" She laughed again, not unkindly. "No, that thought didn't occur to me."
She thought he looked a little hurt at that, but just then Martha returned, ending the conversation. For now, anyway.