Kelly McCreary as Maggie Pierce
First episode (2014): "Everything I Try to Do, Nothing Seems to Turn Out Right" (Season 10, Episode 23)
Latest episode (2020): "Put on a Happy Face" (Season 16, Episode 21)
What she's up to now (2020): Of course, Kelly is still playing Maggie on Grey's and has now appeared in 144 episodes and counting.