I love it when you can stick it right back at them like that.
Friend of mine went through FLETC and was in a role-playing exercise interviewing 'immigrants' on a bus. All spoke Spanish- except that the curve that they tried to throw him was that one of them spoke German. My friend grew up in Germany, so he just effortlessly switched to German. A very English 'Ah, s**t' came out of the grader. :-)
I did something similar in German class. When I had no written report to read from, my teacher insisted I stand at the podium and give my report anyway. My report was on Goethe, and although I had never produced even a first draft, I did study the subject for the report, finding a fascinating analysis by a psychologist on the multi-leveled nature of his writing, as well as some interesting personal history of the man’s childhood and youth which had effects on the stories he wrote and the characters he placed in them. So I went ahead and shared what I had learned. It was the best report in the class.