fancy dress party

An American and a European have the following conversation:

Dave: I’m going to a fancy dress party on Friday night if you want to come with.
Kelly: Sounds great I’ll pack my fancy dress.

Later the American gets a text from the European:

“Kelly, we’re going to fancy dress shopping on Monday so bring your shopping mojo!”
Kelly: [But I already told him I was packing a fancy dress. Maybe he forgot. I’ll tell him later there’s no need.]

Later they have the following conversation:

Dave: Kelly did you get my text? You’ll have to help me out, I need to find a dress for the fancy dress party. Me and some mates will be going as the girls from Sex and the City.
Kelly: [oh he wants to go fancy dress shopping for himself. Wow he’s really taking this fancy dress party seriously…]

Like really REALLY seriously. Like a little too seriously. To the point where there’s something wrong here…

Friday = Halloween :: fancy dress party = ________?

Light bulb.

Kelly: Dave, when you say fancy dress party do you mean like a costume party?
Dave: Yes of course.
Kelly: OOOHHHhhhhh.
Dave: What did you think I meant?
Kelly: A formal affair where I wear a fancy dress.
Dave: OOOHHHhhhhh. So you packed a fancy dress.
Kelly: Yes, and shoes to go with it. What do you think I meant?
Dave: That you brought a costume with you. I thought that was an odd thing to bring with you to France. I just concluded you were really keen on Halloween or something.

Ah English. The same thing happened to my British friend who invited an American to a “fancy dress” party. She went to meet him as a geisha. He showed up in a tux.

I didn’t end up going to the fancy dress party but had I gone I would’ve worn my fancy dress anyways. Had anyone asked I would’ve said:

I’m American. What I’m wearing is a fancy dress. What you’re wearing is a costume.