The former Dawson's Creek star said that she had to undergo a physical transformation to portray the iconic actress with the help of makeup, wardrobe tricks and a few extra pounds.
'I wasn't watching what I ate, let's put it that way,' she told People magazine.'
Actor Don Murray, who played opposite Monroe in Bus Stop in 1956, said that Williams had got the star down to a tee. 'It's very, very accurate,' he said. 'Having spent 14 weeks with Marilyn, I know what she was really like. And Michelle really catches it.'
Meanwhile Williams revealed that one of her favourite things about the star was her natural beauty. 'I liked her kind of simplicity,' she said. 'She was so extraordinarily beautiful, but really quite unadorned.'