Samantha's Wedding Present - S5-E1
Continuity mistake: When Darrin is on the table and growing he is wearing a green suit, when he is full size, he is wearing a blue suit.
Samantha's Wedding Present - S5-E1
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.
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