Scarlett Johansson refused to show hubby her black catsuit

Scarlett Johansson wants to surprise husband Ryan Reynolds with her "tight" 'Iron Man 2' outfit.

The Hollywood actress – who portrays Natasha Romanoff and her sexy alter-ego, Russian spy Black Widow, in the new superhero movie – has refused to show off her black catsuit to her actor spouse because she wants to gauge his reaction when sees her on the big screen.

She said: "I have been so secretive about the suit that I have actually not shown anybody because I want the honest reaction from everybody. The only people who have seen the suit are the crew members. But I have kept it close to my chest, even in my family I haven't shown anybody. I can tell you it's tight!"

However, the 24-year-old beauty – who is known for her busty figure and good looks – admits it was a struggle to make the iconic ensemble both sexy and practical.

She explained: "It's a utilitarian sexy S.W.A.T. type of look. In the comics it's pushed to the extreme and we tried to make it realistic so the material is functional. And obviously I needed to move a lot because I have big stunt sequences. But boy is that catsuit tight!"

Scarlett previously admitted she loved "kicking a*s" in the film, which is based on the Marvel comics of the same name.

She said: "I kick some major a*s! Whose a*s do I kick? Well, you're just going to have to wait and see. You don't really want to know, do you?"

'Iron Man 2' - which also stars Robert Downey Jr. , Gwyneth Paltrow and Mickey Rourke - is due for release in May next year.