Summary

Josh Hartnett recalls the less-than-great advice Matt Damon gave him while filmingOppenheimer. Damon played Leslie Groves in the star-studded ensemble, while Hartnett played Ernest Lawrence. Joining Harnett and Damon was astacked cast that included Cillian Murphy, Emily Blunt, Robert Downey Jr., Benny Safdie, Florence Pugh, Alden Ehrenreich, Scott Grimes, Jason Clarke, and Tony Goldwyn.Oppenheimerwas well-regarded, winning multiple Oscars, including Best Actor for Murphy, Best Supporting Actor for Downey Jr., and Best Picture.

Oppenheimeralso won Oscars for Best Original Score, Best Cinematography, Best Film Editing, and Best Diretcor for Christopher Nolan.

Collage of characters from Oppenheimer

Speaking onThe Tonight Show, Hartnett explains the unhelpful advice that Damon gave to him while they were both working onOppenheimer.

After Hartnett gained 30 pounds for the role, Damon said “You’re never gonnna get that off again, man.” Hartnett explained that Damon has a rule for himself of never gaining weight for roles after the age of 40. Damon continued harping on Hartnett, telling him “you’re just gonna keep growing back to that size.” Hartnett did not appreciate getting the advice after he had already put the weight on. Check out the full quote from Hartnett below:

Oppenheimer Poster

I gained about 30 pounds for the role, and [Damon] was like, ‘You’re never gonna get that off again, man.’ He’s like, ‘You’re gonna spend the rest of your life trying to get that weight off and it’s never gonna come off because your body’s gonna want to get that weight back on. You’re just gonna keep growing back out to that size, and you’re going to try and get it off, but it’s just gonna go back. And he kept telling me, like, over the course of the production. I was like, ‘Thanks, Matt. Thanks for telling me this now. I’ve already gained it.’”

Who Josh Hartnett Played In Oppenheimer Explained

Hartnett played Ernest Lawrence.

Even though Harnett was not a huge fan of Damon’s belated advice, it sounds like there was not too bad blood between the pair. Alongside Harnett, Damon was also a guest onThe TonightShowlater that evening, making for a mini-reunion between theOppenheimerstars. Damon is seven years Hartnett’s senior, making the latter actor a more recent entry into the over-40 club. Even if Damon meant to provide helpful instruction to the younger actor, the delay in this advice was likely unhelpul, as Hartnett’s physical transformation had already begun.

Hartnett made the physical transformation to play thesupporting character of Ernest Lawrencein the film. Born in 1901, Lawrence was an American physicist who won a Nobel Prize in Physics in 1939 when he invented the cyclotron. Oppenheimer met Lawrence while both men were working at UC Berkeley, and the pair of scientists would go on to become collaborators. Lawrence played a key role in the Manhattan Project, assisting with the uranium-isotope separation.

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While Lawrence serves a pivotal role inOppenheimer’s plot, it might not have been entirely necessary for Hartnett to gain 30 pounds for the role. Having Lawrence’s stature being entirely different from Oppenheimer’s is notable, as the contrast makes Oppenheimer look even more gaunt, especially as his years as a scientist aged him. Hartnett’s physical transformation certainly shows his commitment to the role, but perhaps the actor may have wished he’d known about Damon’s advice in advance if gaining weight was not completely necessary.

Oppenheimer

Cast

Oppenheimer is a film by Christopher Nolan, which follows the theoretical physicist J. Robert Oppenheimer, the man behind the atomic bomb. Cillian Murphy will play the titular role, with the story based on the book American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer by Kai Bird and Martin J. Sherwin.