Watch Sia’s Emotional Performance of ‘Unforgettable’, the ‘Finding Dory’ Theme Song

I can’t imagine anyone doing this, Ellen DeGeneres told Sia immediately after she performed Finding Dory’s theme song—a stunning cover of Nat King Cole’s Unforgettable—on Ellen’s show. Ellen, the voice of Dory, asked the singer to do the cover—a powerful choice by Pixar that highlights the Finding Nemo sequel’s plot (Dory, a fish who suffers short-term memory loss, tries to find her family based on the sudden childhood memories returning to her).