per People. The get-together came almost exactly 16 years after the final episode of “ER” on April 2, 2009.But while the night may have been about celebrating Clooney and his “Good Night, and Good Luck” adaptation, he was not the only former “ER” star to hit the Broadway stage in recent months.Margulies, 58, appeared on Broadway in the romantic production “Left on Tenth” last year, and she used her experience with the Theater District to give Clooney some advice about the Great White Way.“I just emailed him and said, ‘I’m so proud of you. You don’t have to do this,'” she told People in October.