First episode (2005): "A Hard Day's Night" (Season 1, Episode 1)

Last episode (2014): "We Are Never Ever Getting Back Together" (Season 10, Episode 22)

What he's up to now (2020): Although he made his last series regular appearance in 2007, Isaiah returned for one episode of Grey's in 2014 as part of Cristina's final arc. After leaving the show, Isaiah went on to star in The 100 as Thelonious Jaha.