Revealing mistake: When Endora turns Darrin into "Ringo"/"Prince Valliant" when he touches his "hair", it moves, revealing it's a wig.
Aunt Clara's Old Flame - S2-E11
Revealing mistake: Aunt Clara levitates her doorknob collection to put it away. As they pass in front of her, the wires used to make them levitate become visible. (00:06:15)
Samantha the Dressmaker - S2-E22
Revealing mistake: When Samantha and Endora are in Paris reviewing models in dresses, the models are frozen because Samantha and Endora are not supposed to be in the dress shop. One of the models, instead of being frozen, is seen blinking her eye and moving slightly.
Follow That Witch (2) - S2-E29
Revealing mistake: When Samantha starts trashing the private detective's apartment, she causes a chandelier to fall onto a coffee table, breaking the table. However, it is easy to see that the table breaks just before the chandelier falls on it. (00:20:10)
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