George Clooney made a surprise guest appearance on “ER” on Thursday for the last episode of departing cast member Julianna Margulies. In the show’s final scene, Margulies’s character, Nurse Carol Hathaway, flew to Seattle for a reunion with Clooney’s Dr. Doug Ross, her former lover and the father of their twin daughters. He literally swept her off her feet. “I don’t know if it’s necessarily smart for me to come back for one scene and, you know, scoop Julianna up and walk out,” Clooney told TV reporters in January, when asked if he would return for a guest spot on the series. He evidently changed his mind, but it wasn’t money that did the trick; Clooney was reportedly paid scale for the 60-second appearance ($596). Last November, the Emmy-winning Margulies turned down an offer of $27 million for another two seasons on TV’s top-rated drama, which NBC has renewed through 2004. Neither star needs career life support: Clooney, who left the show last February, is promoting his new film, the Coen brothers’ “O Brother, Where Art Thou” at the Cannes Film Festival, while Margulies is set to star in the TNT miniseries “Mists of Avalon” as a Druid priestess. “I wanted something as opposite as Hathaway as I could find,” she told USA Today.