Sigourney Weaver Plays A Teen In 'Avatar 2' & Her On-Screen Fam Says She's 'Amazing' At It

Actors play different ages all the time, but how often do you see someone in their seventies playing a teenager in a major movie like Avatar 2?

The new Avatar: The Way Of Water film used motion-capture technology to transform Sigourney Weaver, 73, into a teenaged Na'vi named Kiri, and her on-screen "siblings" say she was absolutely incredible in the role.

"She's a master obviously at what she does, and when she's playing a 14-year-old, she's amazing at it," Jack Champion, who plays the human boy Spider, told Narcity in a recent interview. "When we were in a scene with her it didn't feel like we were working with Sigourney Weaver. It felt like we're working with the character just because she's so good at acting."

Trinity Jo-Li Bliss, who plays Weaver's adopted sister Tuk in the movie, says she was also blown away.

"She's just young at heart," the 13-year-old told Narcity. "And since a lot of her scenes were with us kids, she'd often be around and making us feel like she's our big sis. Sig's a legend."

Weaver played a human scientist who was obsessed with Pandora in the first Avatar film, and while she ends up dying, her Na'vi avatar somehow gets pregnant along the way.

That pregnancy results in Kiri, a teenaged Na'vi with mysterious powers who also happens to be played by Weaver.

It's a bit of an odd move to cast someone like Weaver for such a young role, but she and director James Cameron go way back. Cameron directed Weaver in the 1986 movie Aliens, so it should be no surprise that he wanted to keep her around after killing her off in the first Avatar.

Still, it's not easy to play a teenager when you're closer to being someone grandma, although Weaver clearly put in the work.

Weaver revealed at a press conference earlier this month that she sat in on several high school classes to prepare for the role, all so she could get the right "pitch" to sound like a teen girl.

“I love that I had the opportunity to play a real adolescent,” Weaver said, per Gizmodo.

“There’s a big range of who an adolescent is between 12 and 15, and once I saw that I realized I can let Kiri come out — whoever she is — and combine her with who I was at 14. It gave me so much to work with. And by the time I got there, I just got to enjoy leaving this shell behind and becoming this sometimes-brat.”

Avatar: The Way Of Water is out now exclusively in theatres.