How do you film a make-out scene between a septuagenarian actress and an underage actor?

Sigourney Weaver in Avatar Fire and Ice and Jack Champion in Avatar The Way of Water 20th Century Studios/Courtesy Everett Collection; Walt Disney Studios Motion Pictures/Courtesy Everett Collection

It’s one of the most tender scenes in Avatar: Fire and Ash. A kiss between the Na’vi teenager Kiri and her family’s young human ward nicknamed Spider.

But behind the scenes, the moment was shot between actors Sigourney Weaver (who is now 76) and a then-underage Jack Champion (now 21). Given that portions of Fire and Ash were filmed as much as eight years ago, director James Cameron says Champion was only 15 at the time of shooting.

So how was that scene shot? With a bit of digital help.

“What we did was have Sigourney kiss somebody else and Jack kissed another minor and then we put the two together,” Cameron says. “They played the scene and did everything except the kiss. I think it was OK for Sigourney to kiss him on the cheek. There are a lot of rules around intimacy stuff so that was one of the very few times that we had to do something that was just the tiniest bit inauthentic, but we had to do it because we had to do it that way.”

For Weaver, the experience of playing a teenager in The Way of Water and Fire and Ash had benefits that crossed over into her everyday life. “I think the whole experience of playing a Na’vi, they are so much in their bodies and that changes you,” Weaver says. “I certainly did feel very joyous most of the time. And I think that probably showed physically.”

When asked about working with Cameron in 1986’s Aliens and in two Avatar films, the actress says the famously mercurial director “has always been such a sweetheart to me. He’s such a good guy, and I think he just enjoys what he does.”

Weaver adds: “I’ve worked with so many directors who have a horrible reputation like that, and if somebody screams at someone on the set, frankly, I go up to them and say: ‘If you scream at one person, you scream at all of us. So please don’t do that. We’re all doing the best we can.’”

Cameron has said Fire and Ash could be the last Avatar movie, depending on its box office performance, and Weaver hopes that isn’t the case. “I think [Avatar] 4 and 5 are so amazing. I think the saga should continue because all of them are part of one big story.”

For more from James Cameron’s wide-ranging and deep-dive interview with THR, read this week’s cover story: James Cameron Is Ready to Move Beyond Avatar: “I’ve Got Other Stories to Tell.”

Avatar: Fire and Ash is currently in theaters.