The Wall Street Journal: Normally you play characters who are older than you. Is it a challenge to play a teenager on stage?

Ms. Johansson: It’s really kind of agonizing in some ways to be 17, and I didn’t know if I wanted to go back there. I’m very wary of actors that are in their 20s that are playing teenagers, that play it with this really sort of false adolescence. It’s like a pet peeve of mine. I thought it was going to be an uncomfortable challenge—a challenge, but not a good kind of a challenge—and it turned out that I never thought about it again.

Did you work with a dialect coach?

We did have a dialect coach we’ve been working with. I’m from Manhattan and so it’s not an unfamiliar dialect for me. My mom’s side of the family’s all from New York, and of course they’re Jewish and from different boroughs, so it’s not exactly the same. The Italian Brooklyn accent is sort of particular to the Italians, but it’s similar.

At what moment did it hit you that you’re on Broadway?

I’ve always wanted to be on Broadway, ever since I was a little kid. I always thought I’d be in musical theater. That dream died when I was 12 and became a cynical prepubescent. Over the years I’ve looked at different projects, and I never found anything that I wanted to commit myself to. I don’t know that there was any particular moment where I thought, “Oh, wow, this is it.” To me, it’s still like the work really begins now.

How did you get ready for “Iron Man 2″?

When somebody tells you you’re going to wear a Lycra cat suit, you just go, all right, well I guess I’ll have to start to kind of, you know, wrap my head around that. It’s a very physical role with a lot of stunt work. I immediately had to start training and living a bit of a boring life, a lot of turkey and egg whites and brown rice and, you know, all that stuff that we should all probably be eating every day but love pizza too much to.

You promoted the movie at pop-culture convention Comic-Con. Did you have any strange encounters with comic-book fans in the elevator?

I didn’t see any Black Widows, but I’m waiting. All I have to say—a word of caution to anybody venturing into that latex or whatever cat suit, you know, lay low on the salt.