I've had a lot of movies that didn't get great numbers on test screening, but a lot of times the film was able to survive, or the studio still stayed and supported it.

Studios just sometimes make decisions on their own that you're always flabbergasted by. It just happens that way for whatever reason - not even pointing fingers, it just is.

If you test Iron Man and that audience doesn't respond well, you can be damn sure that there is something wrong with the movie that you have to address. Because they're expecting a certain amount of action, right? They want a hero. There are certain things that have to be compatible with the way the audience is thinking about it. If you take some other film, like No Country for Old Men, you can end up with all kinds of crazy reactions.

I'm emotionally invested in every movie that I do, period, because you've got to make that commitment. You're spending a year, 18 months of your life doing it. I'm invested in all those kinds of pieces. Most of the films I've had in my career have never tested well. I got lucky that sometimes I got supported by studios - or, at least if not supported, tolerated.

I'm fascinated by documentaries, to begin with. Because of the nature of television, as opposed to theatrical, documentaries can be in this long form and take you on a journey.

A lot of people have done things over the years and made fun of people in one way or another. When I was a kid, Vaughn Meader used to do John F. Kennedy. I don't know if that makes John F. Kennedy less credible. He would do the voice, he'd have some silly situations or whatever. I don't know if it made him less presidential because of it.

Some actors are supposed to be very difficult, but I've not found that to be the situation.