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)Jeff Swanson
Other mistake: Samantha is reading a 4-line note from Endora. The paper is semi-transparent and in a shot from the front, we can easily see the writing through the paper. However, after the note is "twitched" into a second, shorter note, there's another shot from the front - and the lettering looks exactly the same as it did before. (00:16:40)Jeff Swanson
Continuity mistake: When Sam and Endora are talking in the foyer, the glass-paneled door at the end of the hallway is closed. When Darrin is seen in the study moments later fighting to get the chair in the closet, the door can be seen against the wall in the hallway, as it would be in the open position. When Darrin stumbles out of the study a moment later, the door is closed again.bixxell
Other mistake: While Gladys Kravitz is standing in front of her house, which is across the street from the front of the Stephens' house, Gladys sees the Stephens' backyard just as Sam zaps a swimming pool and then zaps it away, but since the Stevens' backyard is located behind the house where the living room and dining room are, this would be impossible even for nosy Gladys Kravitz.
Continuity mistake: After Samantha sees the statue talking to her, her expression goes from shocked to annoyed and back to shocked in consecutive shots. Also, her hair is over both shoulders in each of the "shocked" shots but over one shoulder in the "annoyed" shot. (00:24:30)Jeff Swanson
Continuity mistake: When Dave sees Darrin's ad for the community meeting, he suggests a couple of changes, one of them being to add a line saying "and bring your friends". But the ad was shown in close-up shortly before Dave's arrival, and there was already a line saying "Be sure and bring all your friends". (00:13:35)Jeff Swanson