I liked the Roseanne episode where they were talking about changing the actor on Bewitched (didn't they change the character's name, too?) laughing at them for thinking that nodoby would notice. This was just after they had gotten a new actress to play Becky. They also did something else that called attention to the change of actresses, either some comment about her (the character, Becky) not seeming like the same person or some comment when the original actress came back (or was that just sawdust in my JDM®?).