Other mistake: When Abbott and Costello are bringing the first crate (Dracula) into the house of horrors, Abbott tells Costello twice to help with moving the crate. The first time Abbott says to help pull the crate, which is correct. The second time, Abbott says to help push, even though Costello is still pulling.
Other mistake: When Bob Hope is singing Buttons and Bows with accordion, to a sleepy Jane Russell, no-one is driving the horses.