Cast of ER Cast of ER "ER" is an American drama series that aired on NBC from September 19, 1994 until April 2, 2009. The series featured a large ensemble cast that changed dramatically over its long run. The main cast was augmented by a wealth of recurring characters and award-winning guest stars. The original starring cast consisted of Anthony Edwards as Dr. Mark Greene, George Clooney as Dr. Douglas "Doug" Ross, Sherry Stringfield as Dr. Susan Lewis, Noah Wyle as medical student (later Dr.) John Carter, and Eriq La Salle as Dr. Peter Benton. Julianna Margulies guest starred in the pilot as
ER (season 15) transplant. Peter Benton, Doug Ross and Carol Hathaway, Susan Lewis, Elizabeth Corday, Kerry Weaver and Ray Barnett return in various episodes. The series ends with one final multiple casualty incident that brings multiple patients to the ER, and shows that life goes on at County General. The final season included special appearances by departed regular and recurring cast members for the following episodes: <onlyinclude></onlyinclude> ER (season 15) The fifteenth and final season of the American fictional drama television series "ER" premiered on September 25, 2008 and concluded on April 2, 2009, in a two-hour episode preceded by a one-hour retrospective