that one fic where Ten & Donna are in a cave-in (a sumptuous cave, with a lake and all these offerings of food and stuff, natch), and it just so happens to fall on the time when the Doctor has his "mating-time." Ummm, the Doctor's people descended from cave-dwelling animals and so this makes it extra hard for the Doctor, as he's now stuck in the sexy cave of sexins with a sexy Donna. Adult, and a super fun read, with some lovely angst thrown in. I swore I had this bookmarked somewhere, but apparently not.
If you know what fic I'm talking about, please point me in the right direction, as I really want to re-read it. And did anybody else wonder what they used for a toilet? Because that was the one thing that kept bugging me (as it does in all these "trapped" situations, to be fair, not just this fic. Like, I don't blame the author for not mentioning it. Toilets are never sexy.) Probably the Doctor can hold it, but just think of how embarrassing it would be for Donna to have to dig a hole and hope the Doctor doesn't stumble upon it.