It's the end of an era on Grey's Anatomy: Katherine Heigl and T.R. Knight are leaving the show at the end of this season. Heigl, 30, who hit movie stardom with 27 Dresses, has been known to want to leave the series for some time. Knight, 35, is Heigl's BFF and also reportedly seeking other acting opportunities. Heigl famously came to Knight's defense when Isaiah Washington attacked him with homophobic remarks in 2006. Washington later apologized for the incident. (Photo: WENN)