Chyler Leigh will be joining the cast of Grey’s Anatomy this fall. Last season ended with her introducing herself as “Lexie Grey” (watch video below). She even had some major chemistry going on with McDreamy himself, Patrick Dempsey, while at Joe’s Bar. Lexie is the half sister of Meredith Grey. How many freakin’ sisters does Mer have? And why can’t Mer and Derek be happy for once? Sheesh.