"One day, I was like, 'Listen, what can I do? You keep throwing around names, but who do we really want?'" Seyfried told Moviefone while promoting her new film, "Gone," which hits theaters on Feb. 24. "They were like, 'Sarah Jessica Parker.' I was like 'Yes, please. Where is she? What is she doing?' So I called her agent, whom I've never met and asked, 'What can we do to get her involved? We have three days. We need her.' And I emailed her that day and she was on a plane three days later. And she was incredible. She's so good. I'm so grateful that she came in. I wish she'd been there for longer."
Despite her happiness that Parker was able to play the venerable Ms. magazine co-founder, Seyfried was saddened by Moore's departure.
"It was a really hard situation because Demi had worked really hard and she was so prepared and so ready and nobody expected her to not be able to do it -- she didn't either. I knew she wanted to do it, but she knew she had to take care of herself. It's hard when you're pulling for someone, but they can't do it and you have to substitute them. We needed Gloria Steinem in this movie, she was a huge part of Linda's life and such a huge icon."
Seyfried said that Parker is "amazing" in "Lovelace," which also features a cameo from James Franco as Hugh Hefner.
"He came, just in and out in one day. He's really good at embodying different people. He's certainly a character actor in my opinion. I remember him sitting in the trailer and just listening on the headphones to Hef talking. He's really good at mimicking things and it's really important when you come in for just one day and just whip it out. It's really impressive."
Whip it out?
"He didn't actually... oh wait, yes, Hef... no pun intended. There was some whipping," she laughed.
Check back to Moviefone next week for more from Seyfried on "Gone" and getting her father's approval for "Lovelace."