Factual error: In the scene where Bill Murray is listening to "Have Yourself a Merry Little Christmas" the newer, revised lyrics rewritten in 1957 were used. The original lyrics from the original song written in 1944 were deemed too depressing by Frank Sinatra. The lyrics we hear in the movie set during the winter of 1944 were not published until about 13 years later.
Frank Stokes: You can wipe out an entire generation, you can burn their homes to the ground and somehow they'll still find their way back. But if you destroy their history, you destroy their achievements and it's as if they never existed. That's what Hitler wants and that's exactly what we are fighting for.