Blooper

In the opening tilt pan shot of Rockefeller Center, the waterfalls are clearly in reverse.

At the beginning of the movie, which is just after World War I, the Crosby character tells the De Wolfe character to do his Frankenstein routine. The Frankenstein character he does is based on Boris Karloff's 1931 version which some ten years or so in the future. At that time in the movie Frankenstein was just a creature in Mary Shelly's book.

Bing and Fred's Song and Dance Man number was supposed to be one of those "you remember when" moments, however, Bing just happened to have snowflakes in his pocket.