Kazan penned the screenplay for Ruby Sparks, which sees her playing the physical embodiment of a fictional character created by a struggling writer (Dano).
Discussing the movie with Reuters, Kazan said that Ruby Sparks is entirely a fictional tale.
"Paul is an incredibly private person. And I think that if I had written us, he would never have agreed to act in it," she admitted.
"And also, we would make a really boring movie, to be totally frank. We're pretty straightforward, uncomplicated. There's no power play. The worst it ever gets is a fight about what we're going to have for dinner."
Kazan went on to explain that the movie is actually a response to the ways women are often presented in the media.
"I was thinking [for the film] about characters that feel real to me. The best example I can think of is Annie Hall," she commented. "Woody Allen wrote this character that was obviously inspired by women he knew, or a woman he knew, but how much did he define Diane Keaton by writing Annie Hall?
"Or how much did she define him by being who she was, for him to have a muse? And what is the flip side of that? What is her experience?"
She continued: "Then I was thinking about something that feels less well-rounded. I don't want to use a movie example, so I'll take Britney Spears. Britney Spears was both the pop creation and a real person. When we were looking at the pop creation, we were looking at, like, two percent of what the real person was.
"And I started thinking about some movies where the character feels two-dimensional, or their musical taste stands in for their personality. If that's two percent of the iceberg, what does the rest of the iceberg look like? That kind of thinking started to get my brain moving in this direction."
Antonio Banderas, Steve Coogan, Annette Bening and Elliott Gould make up the movie's all-star cast.
Ruby Sparks is now playing in the US and opens on October 12 in the UK.