Camilla Luddington as Jo Wilson
First episode (2012): "Going, Going, Gone" (Season 9, Episode 1)
Latest episode (2020): "Put on a Happy Face" (Season 16, Episode 21)
What she's up to now (2020): Of course, Camilla is still playing Jo on Grey's and has appeared in 189 episodes and counting — in fact, that's more than Katherine Heigl or T.R. Knight ever appeared in.