MADELINE: Hey, party at my house Saturday.
LOUISE: Dress to impress, please.
Dress to impress is a dress code that might be written on a party invitation, like “smart casual”, “black tie”, “costume party”, etc. It’s an especially vague one that leaves most people wondering what the heck they are supposed to wear, but seems be a favourite with rather pretentious people, like Louise. (The only etiquette guide I could find which covered it said it was a sure sign the party would be utterly dreadful, and not to attend). To me, it suggests getting dressed up without actually seeming formal, but not relaxed enough to be smart casual.