Appearing as a tough Navy Seal in new child-care comedy The Pacifier

Why do this film?

Because it felt like a true classic Disney family comedy. It's about a man who's always avoided getting close to anybody. Only now he's forced into having to try to be a caring father figure to five unruly kids. I thought it was a great concept.

Was it easy to put aside your tough guy persona?

Put a nine-month-old baby in Vin Diesel's hands, and you're going to get a big softie. I couldn't help it. I mean, all that formidable, unapproachable stuff went right out the window once I started holding this baby.

Had you changed nappies before?

I had training, believe it or not. But it all came pretty naturally to me Did you do this specifically to combat your action guy image?

It was more to combat the fact that I hadn't done a movie that a family can see. I have nieces and nephews who had been asking, when are you going to do a movie for us, Uncle Vin?

The kids make fun of your pecs.

Has that ever happened before?

I was in an audition 18 years ago for a little infomercial and I was wearing a tank top and I was very, very nervous.

And for some reason my pecs were moving involuntarily throughout the whole audition. And they're like, are you doing that to show off? Is that part of your audition piece? I did get the job though.

What's next?

I just did this film with Sidney Lumet that's the antithesis of The Pacifier. It's called Find Me Guilty. I play Jackie DiNorscio. He's a real guy, 47 years old, who defended himself for three years in court on mob charges.

What are the challenges of playing a real person?

You make this unspoken contract that you are going to represent what that person stood for. I also had to gain 30 pounds, which was a very challenging thing because I've always been connected to my physicality.

The Pacifier is released on May 27