Samantha's Witchcraft Blows a Fuse - S8-E25
Revealing mistake: When Darrin brings the ladder around to the front of the house, it's obvious this is not the actual house but a stage set; the background is obviously a painting and the driveway/garage have disappeared. Further the outside and windows are too narrow to be the actual house. The den is larger than the small facade in the scene.
Samantha's Witchcraft Blows a Fuse - S8-E25
Revealing mistake: When the officers pull away, the shadow of the car is visible on the painted backdrop of trees. This isn't the neighborhood of Morning Glory Circle with the Kravitz House across the street. The shadow reveals it's a stage backdrop. Further, this is basically the same as Allergic to the Macedonian DoDo Bird from Season 3, with the same DoDo Bird costume.
Samantha's Witchcraft Blows a Fuse - S8-E25
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).
Samantha's Witchcraft Blows a Fuse - S8-E25
Continuity mistake: The hole (square cut out) is visible in the carpet before they fall through. Also, when Dr. Bombay "cures" Samantha and she floats, the hole in the floor beside the couch is gone. Dr. Bombay fixed the floor in the next shot (when asked). The floor without the hole is visible when Dam floats up and when Darrin and Bombay walk over to her.
Answer: Larry had been telling Darrin what it means psychologically that Samantha gave the coat away. Larry said giving it away meant she's happy being married but if she liked the coat it means she desires to be single and carefree. So when Darrin sees the coat, he immediately thinks Samantha doesn't want to be married and the fact that she twitched it means (in his mind) she wants to be a single, carefree witch again.
Bishop73