In an early scene, the professor (Richard Purdy) is supposed to pick up a chalk image on his back from leaning against the wall of the building on a drawing of a face done by a boy - but the two drawings face the same way. They should be mirror images of each other.
When Jeff Troy (Robert Sterling) is sitting on the floor outside his wife's room, the bald head of a stagehand appears on the lower right side of the screen.