George Clooney's Doug Ross was the resident heartthrob of hit medical drama ER before departing in season 5; let's break down why he left and his cameo in season 15. Before Grey's Anatomy became America's top medical series, ER reigned on NBC for 15 seasons. Running from 1994 to 2009, the series focused on the doctors working in the emergency room of Chicago's County General Hospital. A good number of major stars walked through those bustling halls during ER's run, with Clooney perhaps being the biggest.
Clooney was one of ER's six original cast members. As the emergency room's primary pediatrician, Ross was known for his rebellious tendencies and, for a time, womanizing attitude. He cared about his patients deeply and would do anything to help them - including going against the rules. As a result, Ross frequently found himself in hot water with his superiors and fellow doctors, most notably Kerry Weaver (Laura Innes). And yet, his relationship with nurse Carol Hathaway (Julianna Margulies) could always be counted on to temper his more destructive decisions.
In ER season 5, Ross' rule-breaking for the benefit of his patients proved to be too much for his County General co-workers. To help a terminally ill boy diagnosed with ALD and his exhausted mother Joi, Ross went against protocol and gave them some pain medication that endangered an ongoing study. Ross got into serious trouble with Weaver and his good friend Mark Greene (Anthony Edwards) when his actions were discovered. Things only got worse when Joi, at the end of her tether, asked Ross to help end her son's suffering. Ross complied, and the fallout of his actions played out in ER season 5 episodes 14 and 15, "The Storm Part 1" and "The Storm Part 2." Though Ross was cleared of any wrongdoing, he ultimately decided to resign from County and take a new job in Seattle.
In real life, Clooney's exit from ER came just when he wanted it to. He was contracted for 5 seasons, and when that came to an end, he opted to pursue more movies. Prior to leaving ER in 1999, he had already nabbed some significant big-screen roles with From Dusk Till Dawn and Batman & Robin. Clooney was interested in expanding his filmography, but he dutifully completed his ER run before doing so. As ER producer John Wells [via SFGate] said at the time of Clooney's departure, "George has done the thing that few people do. That ethic is something that has been less and less present over the last few years." After leaving the series, he notched several more well-received roles, including Three Kings later that same year and O Brother, Where Art Thou? in 2000. His true arrival as a cinematic heavyweight came two years after he left ER in 2001's Ocean's Eleven.
However, season 5 wasn't the last time Clooney appeared on ER. He made a surprise cameo in the season 6 episode "Such Sweet Sorrow" for Margulies' exit, then had a more substantial role in ER's final season. In the season 15 installment "Old Times," Neela Rasgotra (Parminder Nagra) and Sam Taggart (Linda Cardellini) travelled to Ross' hospital to oversee the transport of an organ donation. Along with Carol, who worked alongside him, Ross played a big role in the procuring of the necessary organ. He also took the time to ask Sam and Neela about the state of County General since he left. As it was ER's last season, Clooney's cameo was a fond reminder of how far the series had come, and also an indication that the actor hadn't lost sight of where he started. He even participated in the 2021 cast reunion. Doug Ross was one of ER's most memorable doctors, and his presence was still felt long after he left.