IRON MAN'S GWYNETH PALTROW

SAN DIEGO -- Gwyneth Paltrow, who plays Tony Stark's assistant Pepper Potts in the upcoming Iron Man movie, said the relationship between her character and Robert Downey Jr.'s is "complicated."

"Their relationship is really multi-dimensional," Paltrow said during a recent roundtable interview. "She's very much his confidante, she's the closest person to him. Therešs something very loving in a fraternal way in that she's looking after him.

"But then they have a very kind of bantery, sexy thing happening, too. So it moves into different areas, too."

Paltrow, 34, said her involvement in Iron Man came from simply getting a phone call.

"It was the kind of thing where when I found out the players involved, I was like, 'Definitely, I want to do this,'" she said.

"And Robert was so enthusiastic about it. He called me before, when I was thinking about doing it, and he was so passionate about it. And I'd always wanted to work with him. He's one of my favorite, favorite actors.

"I thought it would be so great to do a movie that was a movie that people saw that was actually also really good with good acting. I though it could be exciting."

Paltrow said she didn't read comic books growing up.

"I was a stranger in this world, but I felt like I was in really good hands," she said.

So how did she get ready for Pepper?

"I prep my movies in the same way," she said. "I read them a lot and I think about the characters a lot, and the kind of path they're on in the universe. And also what I can bring to life through what I'm doing. I sit and listen to music and study my script -- nerd out basically."

An Academy Award winner for Shakespeare in Love, Paltrow isn't completely new to the science-fiction genre, having starred in 2004's Sky Captain and the World of Tomorrow. That film heavily used computer-generated backgrounds, a much different approach than director Jon Favreau is using on Iron Man.

"This one I donšt think I had any green screen at all, and it was really exciting," Paltrow said. "Doing Sky Captain was a lot of fun and it was very surreal being a blue cave for weeks and weeks on end."

With Iron Man, Paltrow was in very real environments like Edwards Air Force Base.

"It was happening with tanks rolling around and F14's," she said. "It was exciting. It was amazing to be in these situations and see all the stuff and watch them blow up stuff."