Wyle left "ER" after 11 seasons. This Thursday, he returns to Chicago's County General for a story arc originally intended to be three episodes until NBC extended the show's run by an additional three episodes.
Several original cast members have paid a final visit to the show so far, with George Clooney and Julianna Margulies scheduled to drop in. Anthony Edwards, who played Dr. Mark Greene, appeared in a flashback. Eriq LaSalle, who played Dr. Peter Benton, directed an episode. Some of the actors who came on in later seasons, including Laura Innes, who played Dr. Kerry Weaver, and Alex Kingston, who played Dr. Elizabeth Corday, made their presence known behind and in front of the camera, respectively.