Caterina Scorsone as Amelia Shepherd
First episode (2010): "Superfreak" (Season 7, Episode 3)
Latest episode (2020): "Put on a Happy Face" (Season 16, Episode 21)
What she's up to now (2020): Alongside her work on Grey's, Caterina played Amelia on Private Practice from 2010 to 2013 — between the two shows, she's actually appeared as Amelia in 211 episodes and counting.