I Thought You Were a Waiter!

"Funny clothes and no food--this will be quite an evening."

Embarrassingly black-tie. From here.
A bit of tongue-in-cheek from Mrs. Martha Levinson on the second episode of the third season of Downtown Abbey. We're way behind and like it that way. So many etiquette issues and plot twists that rely on clothing and British identity in this episode. Class, inheritance, new love...so many endangered species.

I imagine most of the audience couldn't tell the difference anyways, so they lay it on a little thick, but the extreme similarity of white and black tie dress in the modern viewer's perception is part of the joke as well as the tension. Who is proper, and who decides what that means at any given point and in every situation? How important is it to know the answer to those questions?