Revealing mistake: The hallway that leads to the den and the back door of the kitchen has a door at the end of it, when this door is opened we see what looks like pine trees and mountains, we know that the Stevens have neighbors on that side of the house, so that when the door is opened you can blatantly tell that it is a picture.
Revealing mistake: In several episodes, the window over the kitchen sink is shown from the outside, while snoopy people look in. The window shown in these exterior shots is far too low to be the same window that is over the Steven's kitchen sink, which is shown in many shots looking out.Super Grover
Revealing mistake: In addition to Samantha, Elizabeth Montgomery also played Serena. In scenes where both characters appeared, Elizabeth would face the camera and play one character and another actress, Melody McCord, would play the other with her back to the camera. But in this scene, when Mr. Beams tells Serena she has a luncheon date with her intended at the rotisserie, Melody (portraying Samantha), with her back to the camera, inadvertently turns her head, revealing her face. (00:07:20)Jeff Swanson
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
Revealing mistake: After Samantha restores the leprechaun's power he walks into the backyard, and when Endora, who's on the roof, uses her powers to have him float up to join her, the wire cables can be seen giving him the needed boost upwards. Later, the cables can be seen again when Sam lifts him up in the living room. (00:09:40)Super Grover
Revealing mistake: At the end of the episode, during Serena and Samantha's second meeting with Mr. Beams, in the wideshots of the two women sitting on the couch and also when they're both poking their heads through the doorway, Serena's body double actually appears face-forward. Additionally, in the closeups of Serena and Sam on the couch, both are played by Elizabeth Montgomery, and we can see the wall's color difference behind them due to the use of the split-screen technique. (00:22:25)Super Grover