"I think emotionally, this is way rawer than the stuff she did in Monster which was also brilliant, but in Monster she doesn't look like herself so now there is no artifice. She is channeling this other thing through her without judgment and it's kind of astonishing to watch it."
Writer Diablo Cody agrees with Oswalt, although she admits there was some concern to whether or not an audience could believe a "supermodel" like Theron could ever pass as a small-town girl.
"I had always imagined Mavis as an attractive tall blonde, but at the same time, Charlize is in a completely different category of beautiful," says Cody, who says her doubts quickly faded as they began filming. "She is so amazing, she is such a chameleon that she pulled it off flawlessly."
Young Adult arrives in theaters December 16, 2011.