The dangers of the double negative…
ATC: Did you get your numbers?
Airline: [Somewhat garbled] Negative.
ATC: Was it “Negative?”
Airline: [Again, rather garbled} Affirmative.
ATC: So … “negative,” or “affirmative?”
Airline: “Affirmative” for “negative…” [The other guy in the cockpit can be heard chuckling in the background.]