Season 1, episode 2: "The First Cut Is the Deepest"
It's easy to hit snooze between a season's premiere and finale, but this understated episode offers a rich fountain of character development. We see Izzie acting on a kind heart and sneaking out supplies to help an undocumented immigrant, Meredith trusting her intuition and saving a baby's life, and Burke defending his credentials to be chief, only to be called out for his arrogance. We also see the interns also forming a bond over their utter cluelessness, touching on the vulnerability and intimacy at the heart of the show. Even Meredith opens up to her new friends, despite her spiel about maintaining boundaries. This episode doesn't quite emotionally wreck us as many Grey’s Anatomy episodes do, but it definitely deserves recognition for featuring nuanced character development.