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 Kellie Martin Lucy Knight Actor Jorja Fox Actor Paul McCrane Robert Romano Actor Bill Henderson Charley Barnes Guest Star Kyle Chambers Ricky Abbott Guest Star Dick Miller Mr. Ackerman Guest Star William Bumiller NASA lecturer Guest Star Terri Hanauer Mrs. Haggerty Guest Star Ron Fassler Aaron's Father Guest Star Valerie Mahaffey Joi Abbott Guest Star Carl Lumbly Dr. Graham Baker Guest Star Emily Wagner Doris Pickman Guest Star Michael Crichton Executive Producer John Wells Executive Producer