Revealing mistake: Paul Lynde is supposedly "in" the mirror near the front door, but as he waves his arm to cast a spell, the shadow of his arm waving is visible at the far left, revealing he is actually standing off camera at a spot where his reflection is visible. Elizabeth Montgomery also briefly glances at him. (00:02:25)
Continuity mistake: When Larry comes to the Stephens' house, he looks at Dr. Bombay and asks "who's that?" In Season 3, There's Gold in Them Thar Pills he met Dr. Bombay and partnered with him to sell Dr. Bombay's pill to cure the common cold.
Other mistake: This is a remake of season 1 episode when Paul Lynda makes his first appearance as Harold the driving instructor for Samantha.
Suggested correction: This is trivia at best, but the episode isn't really a remake of an earlier episode. Here Samantha teaches Uncle Arthur (Lynde) to drive and in season 1 Harold (Lynde) taught Samantha to drive. But the same actor playing multiple roles in a series is never a mistake.