Rosie Huntingdon-Whiteley helped change the feel of the 'Transformers' franchise.
He said: "My casting woman said, 'Ya know, there's something exciting about Rosie, I'm telling you Michael, this girl could be a star.
"She's also really polite - she says thank you and good morning. It helps the movie by recasting. There's something nice about the spark of a new relationship. I think it helps the movie."
Michael also revealed he was dubious about shooting the movie in 3-D, but was convinced by 'Avatar' director James Cameron.
He added to Movie Hole: "Jim was like, 'Right, you better shoot in 3-D. He was like 'You gotta try it, you gotta try it.'
"But as you've probably read, I was hesitant. Took me about a year to research 3D properly before I decided to use it. I'm an Old School film guy - I still hate shooting digital; whatever any director tells you, digital is never as good as film - and I was hesitant about this new toy, and that's what it is, a new toy."