Blown movie lines - Torn Curtain

In the underrated movie Torn Curtain, American scientists Michael Armstrong (Paul Newman) and Sarah Louise Sherman (Julie Andrews) meet up with East German scientist Gustav Lindt (the excellent actor Ludwig Dorath) to pump him for a secret formula (the MacGuffin.)

They're at an upscale party and a waltz is playing.  Lindt is a little tipsy and enjoying himself, and he says:

Lindt: The Vienna Waltz. Did I tell you my sister Emily was knocked down by a tram in Vienna? (sings along to the good bit - about 0:54 in the link below.)

Why is this a blown line?

Because there is no such waltz. There are various waltzes with "Vienna" in the title, but the particular waltz in question is the Emperor Waltz.  It would indeed be unfortunate if poor Emily was knocked down by the Emperor...

Hitchcock directed a film about Johann Strauss, Jr.: Waltzes from Vienna, and Ludwig Donath was himself Austrian, so this mistake is surprising.

As an aside, it was this movie (in particular the blackboard scene) that stimulated my youthful interest in mathematics.  A couple of people arguing over weird chalk symbols and one of them says "it would blow up!" - that got my attention.