Desk Set (1957)

Continuity mistake: When Katherine Hepburn and Spencer Tracy are on the roof eating lunch, she opens and eats her sandwich over and over again.

Bunny Watson: I don't smoke, I only drink champagne when I'm lucky enough to get it, my hair is naturally natural, I live alone... and so do you.
Richard Sumner: How do you know that?
Bunny Watson: Because you're wearing one brown sock and one black sock.