Apparently the real Maria Von Trapp, on first being apprised of The Sound of Music's strolling-across-the-Alps finale, commented, "Has no one associated with this show ever looked at a map?"
Also apparently not true: that Goebbels dropped by Fritz Lang's flat one evening, offered him the job of Chief Nazi Filmmaker, and Fritz said "Excuse me, I have something on the stove," went out the back door, and took the next train to Paris.
But if you mix the two, you get something that is true: The Trapps were asked to sing for Hitler's birthday and declined. They hopped a train to Italy within days and from there sailed to America.