Anthony Edwards Dr. Mark Greene Actor George Clooney Dr. Doug Ross Actor Eriq La Salle Dr. Peter Benton Actor Noah Wyle Dr. John Carter Actor Julianna Margulies Head Nurse Carol Hathaway Actor Gloria Reuben Jeanie Boulet Actor Laura Innes Dr. Kerry Weaver Actor Alex Kingston Dr. Elizabeth Corday Actor Maria Bello Dr. Anna Del Amico Actor William H. Macy Guest Star Gerald S. O'Loughlin George Guest Star Tracy Vilar Doris Guest Star Lisa Edelstein Aggie Orton Guest Star Brent Jennings Nat Guest Star Peter Birkenhead Bite Victim's Father Guest Star Jessie Nelson Bite Victim's Mother Guest Star Darnell Williams Theo Williams Guest Star Nicki Micheaux Mrs. Williams Guest Star Justina Machado Ms. Cruz Guest Star Nick Offerman Rog Guest Star Michael Crichton Executive Producer John Wells Executive Producer