 The " Counterfeit " story features the character Lisa undergoing plastic surgery to become Tessa 's double . Lisa was played by Meilani Paul before the surgery and by Vandernoot after it . The producers wondered whether the story needed to explain the change in Lisa 's voice , as she would be played by a different actor . They considered suggesting that her voice changed because of the surgery , then decided that Lisa would have voice training . After her operation , Lisa speaks with Vandernoot 's voice when posing as Tessa , and with Meilani Paul 's voice when the character was not acting . This was achieved using automated dialogue replacement during post @-@ production . 
