Sydney Chandler does such an amazing job in Alien: Earth of duplicating the mannerisms of a child in an adult’s body.
(The backstory is that she’s a terminally-ill kid transplanted into a synthetic body. Since synths don’t grow, they migrate her consciousness into the body of fully-adult-mimicking synthetic body.)
She gives my favorite performance I’ve seen lately. Sydney manages to perfectly reproduce the gawky impulsiveness and awkwardness of a ten-year-old without overdoing it or seeming like an adult pretending to be a kid. She just gives total “kid” aura. It’s quite amazing.
Like, damn girl, leave some talent of the rest of us.