According to "Don't Look Up" director Adam McKay, Leo balked at the idea of a naked Meryl — because you just don't make film royalty do that.
In the disaster satire, the 21-time Oscar nominee plays U.S. President Janie Orlean, who, at one stage, ditches her clothes and even flashes a "tramp stamp" — which Meryl had absolutely no problem with.
"She is fearless," McKay told The Guardian, adding that "yes, that is a body double."
"But you know who had a problem with it? Leo."
"Leo just views Meryl as film royalty … although maybe royalty is not a compliment … but as such a special figure in the history of film," the director explained. "He didn't like seeing her with the lower back tattoo, walking for a second naked."
"He said something to me like: 'Do you really need to show that?' And I was like: 'It's President Orlean; it's not Meryl Streep.' But she didn't even blink. She didn't even bring it up."
The film sees DiCaprio and Jennifer Lawrence play a pair of low-level astronomers who must go on a giant media tour to warn mankind of an approaching comet that will destroy planet Earth.
The stellar cast also boasts Cate Blanchett, Timothée Chalamet, Tyler Perry, Mark Rylance, Jonah Hill and Ariana Grande.
McKay admitted that while he sort of had Streep in mind for the role, he never dared think she would actually sign on; but when she did "it then became just a cascading effect," and her fellow A-listers flowed in behind.
"So yeah, it got slightly embarrassing," he said. "At one point I almost found myself apologizing to my director friends."
"Don't Look Up" is an obvious allegory on the ongoing ignorance surrounding climate change; McKay has previously tackled real world topics such as the 2008 financial crash in "The Big Short", and Dick Cheney's vice-presidency in "Vice".
Elsewhere in the interview, McKay said he got two interesting reactions from the Cheney family in the wake of the latter.
"I got two reactions," he recalled. "A friend of Christian Bale was at a party and said to Dick Cheney: 'I know Christian Bale.' And Cheney looked up at them and said: 'Well, you tell Christian Bale he's a dick." And Christian’s friend laughed, and Cheney said: 'I'm not kidding.'"
"And then the second reaction, and you've got to judge if this is me thinking too much of our movie, but I think it's pretty odd that Liz Cheney just came out for gay marriage," McKay continued. "And I do know, from seeing her timeline on social media, a lot of people gave her a hard time for betraying her sister [Mary, who is a lesbian]. For a Republican candidate in the state of Wyoming to come out publicly in support of gay marriage … there is no political advantage to doing that. I just found that very curious."