When Luna is walking in the foggy night, her head hits some of the fibers simulating the fog and lifts most of the misty background that surrounds her.
When the professor first tries to hypnotize Baron Otto, there is a reflection of the candle he is holding which cannot be explained.
The character of Jan (pronounced as it would be in Prague as "yan") is referred to by the English pronunciation inexplicably by one character a few times before returning to pronouncing it correctly.