In every film with military aircraft–particularly from the 1960s and earlier–I’ve heard the pilots say “Roger Wilco.” I never knew what it meant, but it lies in the military phonetic alphabet.
Because so much of military communication is over a radio, and often one where it’s hard to hear, it’s easy to mix up letters. So each letter has a word associated with it that can’t be misheard. R was always Romeo to me, but it turned out another word was universally used until 1957. You can read about it here.