Continuity mistake: When Fritz is trying to steal a brain, he gets scared by a skeleton, which he grabs down, causing it to bounce up and down (since it is hanging from a hook up on the ceiling). But in the next shot, the skeleton is hardly moving. Yet when Fritz realizes he has dropped the brain, the skeleton is bouncing up and down again.
Continuity mistake: Just before Victor enters Elizabeth's room, there is a shot of a picture of Henry Frankenstein, which is at the same height as a lit candle. But in the next shot, when Victor and Elizabeth walk by the table (the one on the far right of the screen) where the picture stands, the candle now appears to be much higher than the picture.