It takes a special kind of writer to turn E. L. James's erotic bestseller, Fifty Shades of Grey, into a fan-pleasing film adaptation. British screenwriter Kelly Marcel was specifically chosen for the job. Her biggest task was making the jump from such works as Steven Spielberg's Terra Nova and the Mary Poppins-inspired Saving Mr. Banks, to Christian Grey's Red Room of Pain.

Vanity Fair reports that James herself chose Marcel to write the screen adaptation of her novel. Marcel's resumé showed her ability to pay attention to character, an important component when it comes to transforming unique characters like Christian Grey (Jamie Dornan) and Anastasia Steele (Dakota Johnson) from naughty characters on a page to racy, realistic adults on a screen.

"I am a character writer... I basically like to follow people," Marcel told Vanity Fair.

Writing for Fifty Shades of Grey is a special challenge, however, given the large success of the book and the dedication of its fans. Still, Marcel says her creative process was no different.

"There is a book ... there [was] a template to follow on that one. It's all laid out. So no, I didn't worry about it," Marcel said. "I had E.L. James with me every step of the way, and she is very, very tied to her fan base and she really wants to make the film that they'll be happy with."

James is reportedly very involved in the movie process, something that helped Marcel stay true to her template.

"[James] knows her fans," Marcel continued. "She knows her audience. She knows her book, so having her around was invaluable because you can't really go wrong when the author is overseeing it. I think it was a great thing."

Considering how much hype surrounds the film, Marcel was "surprised" at how "lovely" and "easy" her colleagues were.

"Everyone was kind of allowed to do their job, which you don't think is going to happen when it's so enormous like that," she said.

Fifty Shades of Grey is certainly one of a kind, being the book that popularized the genre of "mommy porn." So what did Marcel watch in order to educate herself for the job?

"Apart from the porn? Lots of porn," she joked. "No, there wasn't really anything. I didn't for Fifty Shades. For Saving Mr. Banks, I did watch a lot of Mary Poppins."

Marcel's next task is taking what she learned from writing the Fifty Shades of Grey screenplay and somehow applying it to her next job: rewriting The Little Mermaid.

"Christian Grey had traumas in his childhood and lives his adult way because of those," Marcel explained. "The Little Mermaid is also a kind of tragic, love-lorn figure, so they are all people that just have extraordinary stories that spin around them."