Be it Ever So Mortgaged - S1-E2
Revealing mistake: When Gladys is looking through the window, you can see part of the facade cross bracing.
I, Darrin, Take This Witch, Samantha - S1-E1
Revealing mistake: After the hairbrush comes to Samantha, she starts to brush, and you see the lights reflect off the wires used for the gag.
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