Hippie, Hippie, Hooray - S4-E21
Continuity mistake: In season 4 episode 10 (That Was No Chick, That Was My Wife) Louise and Larry met Serena when Sam was explaining why she was home and not Chicago. Then in this episode neither Larry nor Louise know about Serena.
Answer: The original diamond and white gold heart necklace was given to Elizabeth Montgomery by her then real-life husband, William Asher, who also directed the show. She wore it in nearly every early episode. When the necklace was lost or stolen about mid-way through the series, Montgomery had two replicas made from rhinestones. She wore either one of those for the rest of the show's run.
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