: Meredith, Cristina, Izzie, and Alex transition from interns to first-year residents, each managing their own group of interns.
: This season was shortened to 17 episodes due to the 2007–08 Writers Guild of America strike, leading to a more episodic feel compared to earlier seasons. Major Plot Arcs Favorite Moments from Grey's Anatomy Season 4
: The season introduces Lexie Grey, Meredith’s eager half-sister, whose presence forces Meredith to confront her complicated family history.