"I think it would be fun to see people naked," laughs Charlize Theron, currently starring opposite Will Smith's boozy superhero in Hancock. If Smith's Hollywood box office record is ample proof that he can walk on water, then Theron has clearly given plenty of thought to what her own super power would be. "You know, it would be fun to walk down the street and see people nude without them knowing. I guess that's the element that makes a difference - them just not knowing. Because when we're nude, we tend to suck it in. Just to see some dude taking the garbage out.maybe I'm taking this too seriously! But seeing everyone naked could also be a bit scary, so I think you'd have to have a sense of humour about it."

Will Smith, however, told Theron that he'd like a slightly more sedate super power. "He'd like to read people's minds," the actress says. "But I don't know about that one. That would probably be my least favourite one to have, because it would make me so paranoid. I'd be like, 'Wow! Do they really think that?'"

If Theron's 2004 Best Actress Oscar for Monster effectively wiped out her old lightweight "eye candy" image, she's never looked back, going on to star in the highly acclaimed dramas North Country (where she played a female mine worker who takes her sexual harassment case to the courts) and last year's In The Valley Of Elah (portraying an overworked detective who helps Tommy Lee Jones uncover the mystery of his soldier son's death on US soil after a tour of duty in Iraq). Filming an action comedy like Hancock, and co-starring with funny guys Will Smith and Jason Bateman, would seem like the perfect break from so much earnestness, although the 32-year-old actress takes offence at any suggestion that her job here might be easier and also considerably better paid. "Oh right, yeah, it depends on how much they pay me - the more they pay me, the more I give," Theron says whippet-fast with good humoured sarcasm. "No, you give it all - you have to. I don't think anybody ever holds back.well, I'm only speaking for myself. I don't want to do something which I feel I can do with my eyes closed; that would be my worst nightmare, because it's very time consuming to make a film. And if I had to get out of bed every morning and go do something that I didn't feel challenged by, I would probably kill myself.this is getting very heavy with images of my hanging myself," she grins.

But surely she seeks to find a balance between heavy drama and light comedy? "No," Theron replies. "And Will Smith and I talked about this. Will might be the one person who can actually change this in our industry. We have been so compartmentalised as actors - we go in and do the really small independent films that are critically acclaimed and award winning, and then people think that you go and sell out and that you only do the big movies because you need to get a big pay cheque. They think that the material is not so great, and it's evident that you're doing it for the money. But what I think is so great is that Will is working on the big budget films, while at the same time he has a real hunger for wanting the material to be good. He might be the guy who can change that for us, where we don't have to go and do smaller budget films and work for free to do good quality work."

Ask how she feels about the fact that she's been regularly anointed as "The Sexiest Woman Alive", and Theron grins and repeats in a deep voice, "I feel like The Sexiest Woman Alive. Oh yes! But seriously, everything in life has to be taken with giant heaps of salt. Look, it's a great compliment. They could have said something a lot worse, so I'm not jaded about that. It's really sweet, but there's no such thing as the sexiest woman alive, so I don't walk around aiming to live up to some standard. That would be impossible."

Hancock is released on July 3.