Revealing mistake: Most of the posed, fake displays in the ape's Museum of Natural History contain real people who are slightly moving if one pays careful attention. Especially noticeable are those posing with objects held in - or above - their hands.
Revealing mistake: Just after the scene where the doctor asks Columbo to switch off the light before leaving, the detective does so, but it can be seen that both light switches are down before he does this, and that they are still both in the down position after he "switches off" the light.
Revealing mistake: Rosemary crosses 5th Avenue as she goes looking for a bookstore to find more material on witches and a lot of bystanders can be seen staring at the film crew. (01:36:10)