Charlize Theron famously gained 30 pounds and wore fake teeth to play real-life serial killer Aileen Wuornos in “Monster,” but she claims that portraying former Fox News host Megyn Kelly in the upcoming “Bombshell” was even more difficult.

The women who brought down Roger Ailes, the Fox News Chief accused of sexual harassment and assault, are the focus of a new film directed by Jay Roach. It features an all-star cast: Kelly is played by Theron, Ailes is played by John Lithgow, Gretchen Carlson is played by Nicole Kidman, Kayla Pospisil is played by Margot Robbie, and Kate McKinnon is a Fox News crew member. Even if you already know how the movie ends, the trailer will captivate you.

According to People, Theron said, “This was harder,” before mentioning Kelly’s fame.

She went on to say, “She’s incredibly well-known. I’ve never played anybody on that level. I’ve played real people that nobody knows about so there was less pressure when I did those.”

She continued, “I was just really scared, too, because I honestly knew her so superficially. She’s conflicting… This was harder [than Monster]. You forget sometimes — all of us do this — we think we know people, we have our preconceived ideas of them. As an actor, you have to have that ability to put all of that aside and do research, and to actually find out about somebody.”

Theron went on to say that her initial reservations about acting in Bombshell were alleviated after she realized the film chronicles a year at Fox News in general rather than concentrating on Kelly specifically. “Once I got past that, that year in her life was incredibly interesting, and felt to me like a story worth telling,” she said.

After playing Kelly, Theron expressed “empathy” for her in March.

At the SXSW premiere of her film Long Shot, Theron told Variety, “I didn’t know how complicated her situation was. I think for a lot of people, they didn’t understand why she just didn’t speak up. She was in a complicated place, and as a human being, I have empathy for that. And I don’t think a lot of people truly understood that.”

“Bombshell,” which opens in cinemas in December, is anticipated to propel Theron and her co-stars Nicole Kidman and Margot Robbie into the Oscar sweepstakes.