Josh Hartnett gained 30 pounds for his role in "Oppenheimer." His costar Matt Damon warned him it would be difficult to lose the weight after filming wrapped. "He was like, 'You're never gonna get that off again, man,'" Harnett recalled Damon telling him. Too bad he didn't warn his costar Josh Harnett before he decided to gain 30 pounds to play the famed physicist Ernest Lawrence in "Oppenheimer." "He was like, 'You're never gonna get that off again, man,'" Harnett recalled Damon saying on "The Tonight Show."

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Persons: Josh Hartnett, Oppenheimer, Matt Damon, Harnett, Damon, —, Josh Harnett, Ernest Lawrence Organizations: Service, Business