Bridget Jones's Diary (2001)

Factual error: No British woman measures her weight in pounds only - always stones and pounds, or kilograms (a concession to the Americans but it sounds really odd to us Brits). Yes, in the American printing of the book it's always only pounds as well, but that's for the same reason, and still wrong.

Mark Darcy: I don't think you're an idiot at all. I mean, there are elements of the ridiculous about you. Your mother's pretty interesting. And you really are an appallingly bad public speaker. And, um, you tend to let whatever's in your head come out of your mouth without much consideration of the consequences... But the thing is, um, what I'm trying to say, very inarticulately, is that, um, in fact, perhaps despite appearances, I like you, very much. Just as you are.

Trivia: When Mark Darcy returns from America in order to kiss Bridget, she asks him: "So you're not going to America then?" and he says "So it would seem." Incidentally that is also the last line of the BBC version of Pride and Prejudice, which also starred Colin Firth. Helen Fielding, the author, openly admits that she got her inspiration for the story from Pride and Prejudice. It was written for TV by the same bloke, Andrew Davies, who helped write the screenplay for Bridget Jones's Diary.

Question: I never understood the joke about the scene where Bridget was wearing the black dress and white undies. Everything looked fine to me, but she looked all embarrassed in front of the guy she was with when the two were fooling around. What joke did I miss?