While I appreciate that the actors really enjoy playing doppelgangers, usually it's such an annoying storyline. I think probably the only "doppelganger" storyline I liked was Charles Shaughnessy playing both Shane and his twin brother Drew. And of course, I loved Marlena and Samantha, but they were two separate actors playing the roles, not Deidre Hall playing both Marlena and Samantha. (except one time years ago when Marlena was sick in a hospital bed and imagining Samantha talking to her while standing by the bed)
I think it's different when one actor plays twins and they are both doing their thing (Shane/Drew), but when it's an evil lookalike, the storyline is always that the original character is held captive somewhere while the evil lookalike is running around town creating havoc. (Kristen/Susan, Bonnie/Adrienne, Arnold/Rafe, Hattie/Marlena, Kristen in a Nicole mask, Andre/Tony, Princess Gina/Hope, Mitch/Bo.)