Airing for roughly fifteen years, ER saw the death and abrupt exits of many beloved characters, most notably Dr. Mark Greene ...

We rank the most shocking episodes from NBC's legacy medical drama ER, from "Freefall" to "Be Still My Heart." ...

was Dr. Greene's daughter as well." He adds, "I never made that connection. That's crazy. I don't know that anybody ever did." Related: George Clooney Says He's 'Still Close' with His 'ER' Costars ...

Noah Wyle looks back on his time playing Dr. John Carter on 'ER' and his crossover with 'Friends,' revealing to PEOPLE he was ...