In film and television, it’s common to see characters at various ages and stages of their lives, portrayed by different actors—but, in the vein of Barry Jenkin’s Moonlight, it’s much less common to see multiple iterations of a character, each as fully realized as the next. Such is certainly the case with National Geographic’s Geniusexecutive produced by Ron Howard and Brian Grazer of Imagine Entertainment, alongside Oddlot Entertainment’s Gigi Pritzker and Rachel Shane—in which Johnny Flynn and Geoffrey Rush are two equally brilliant sides of the coin, portraying the younger and the elder Albert Einstein.

“I’m in my sixties now, and I thought it was time to embrace sexagenarian-type roles. You know what I mean?” Rush said, sitting down alongside Flynn at Deadline’s Tribeca Studio. “I’ve been fortunate in the theater recently to have played Lady Bracknell, and I did a King Lear with a company I’ve worked with before in Australia. So when Einstein comes along and you’ve got ten hours to tell the story, it’s a scary possibility, but it’s the leap you kind of want to make.”

National Geographic/Robert Viglasky

Discussing the project, both actors noted that the Einstein of Genius is not the Einstein we know—or think we know—but rather, a more fully realized human portrait of one of the world’s greatest minds, investigating his life, his loves, and his regrets. “We had to take that two-dimensional sort of silhouette of the guy with the wild hair, the absentminded, archetypal professor that we know—we think we know—and kind of scrap that,” Flynn said. “In my case, I was kind of imagining a young, passionate guy who was burning with curiosity and ideas, and saw the world in a very different way, and kind of had to smash through a lot of resistance to get these ideas out there.”

Indeed, the young, rebellious Einstein did face quite a lot of resistance, because, as Flynn puts it, “He was telling people that the way they saw the world was fundamentally wrong.”

National Geographic/Dusan Martincek

In Tribeca on Friday, Rush discussed the attributes of Einstein that stood out most to him, outside the realm of his scientific contributions. “I can tell, because I was lucky to see a lot of film footage of the age group, from the ‘40s to his seventies—he seemed to have like Groucho Marx-level of wit,” Rush said. “He could make reporters laugh as soon as he met them, and really enjoyed communicating in that way with people.”

Following a screening in Tribeca this past Thursday, Genius will premiere on Nat Geo on April 25. The anthology series was recently renewed for a second season, with the subject matter of the second installment yet to be announced.

To view Deadline’s conversation with the two Einsteins, click above.