Character mistake: In Season 3, Witches and Warlocks are My Favorite Things, Maurice says he won't stay for Tabitha's testing coven because it's "women's work" but in this episode, when Adam is finally tested, he arrives and says he wouldn't miss seeing his grandchild being tested.
Revealing mistake: Darrin casts a shadow revealing painted sky background when he goes out to pay cab. Later, when he goes out to get in helicopter the neighborhood is not the neighborhood we normally see outside the Stevens' house. There's an Amoco gas station across the street.
Continuity mistake: When Samantha opens the door, you can see the 3 pictures by the door. The middle picture is straight. When the camera cuts to Samantha and Aunt Clara and returns to Larry at the door, the middle picture is crooked... a necessary plot point to distract Larry from the desk in the stair case.
Other mistake: The exterior scene when Clara parachutes in is not the real outside we see throughout the show with neighbors including the Kravitz across the street and fewer trees...and no pine forest. Also, it's obvious Marion Lorne, who was about 80 at the time, was sitting on a swing like apparatus being lowered... understandably.
Other mistake: When Darrin is first shrunk we see that his clothes are unaffected by Endora's spell (they don't shrink). So, when he was popped back to normal heights, his clothes shouldn't be affected, and he would burst out of them. We already know his suit changed colors.
Other mistake: When the police pull up outside the Stephens' home, it is a set shot with fake background. The "road" doesn't match the outside of Stephens' neighborhood shown throughout the series with the Kravitz house across the street (and not a pine tree forest as shown here).