You know, the one where Petrie says this is the first time Spike's ever had sex with Dru, and we all say "After 20 years? Are you on crack, Petrie?" (I had a post saying pretty much that a year or so ago when it came up in discussion on someone else's LJ and I went "Er?"
Except, er, he doesn't. He says "This is the first time that he, you know, has Drusilla. I think that in their gang, Angelus has all the juice, and Spike just gave himself a promotion."
Which, to me, comes off as Petrie meaning that it's the first time Dru is his, that he has her as in has her full attention, that he's not just a substitute for when Daddy's too busy. (Or, since it's the Boxer rebellion and Angel's been missing for two years, a substitute for when Daddy buggers off to who knows where...)
The line is much more ambiguous than the fannish bibble about it led me to believe. To the point where were I hearing it without that interpretation already in my head, I'd never even consider that he might literally mean "It's the first time they've had sex."