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Doug and Carol (George Clooney and Julianna Margulies), ER
Carol was supposed to die in the pilot. Thank goodness producers changed her fate or we would've missed out on one of the most complicated and compelling small-screen romances. The playboy doc had his way with many women, but it was always Carol, who saw beyond his bravado, to whom he kept coming back. George Clooney and Julianna Margulies' off-the-charts chemistry was also hard to deny. The actor's surprise return in Margulies' final episode was one of TV's best-kept secrets and made for the sweetest swan song ever.