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Anthony Edwards played Dr. Mark Greene for eight seasons before leaving after his character—and this is a spoiler alert for a show that premiered more than 20 years ago—died from a brain tumor. Edwards returned for the final season in a flashback episode. Following the end of ER, he starred in Zero Hero, directed My Dead Boyfriend and recurred on Law & Order True Crime: The Menendez Murders. He had a role in Netflix’s Designated Survivor season three.