An old man appears with children following him. This is supposed to be pedagogue Janusz Korczak. It appeared as if he was just wearing a suit and a Jewish arm band. In the Warsaw Ghetto, Mr. Korczak never wore an arm band and wore his WWI Polish Army Uniform, both as acts of defiance. He was beaten and almost put to death (he had connections) for not wearing an arm band so having one on in the movie is inaccurate.
Adrian Brody insisted on learning to play the piano himself because he detested the idea of him being in a long shot pretending to play the instrument and then the camera showing someone else's hands on a close up shot actually playing. He said he hated that, not just for him, but on any other film that had such a scene. So he went and took lessons, practicing for hours on end.