New action-comedy Tropic Thunder hits cinemas this weekend and its stars spill the beans.

Ben Stiller who stars and directs the film has been working on the script for a decade.

He said: "It is an idea I have been working on for a long time. I've been playing around with it and trying to figure out how to make the script work for a while.

Stiller added: "And then we figured out how to make the movie. There were quite a lot of parts to the movie."

In the film Stiller plays actor Tugg Speedman who is disappointed that his previous portrayal of a mentally disabled character called Simple Jack failed to win critical acclaim.

Tom Cruise, Nick Nolte, Jack Black and Robert Downey Jnr also star in the action-comedy.

Black said of Cruise: "Cruise and I never shared the screen, but I did see him at the read-through of the film a couple of years ago and he is very charismatic and funny."

Downey Jnr said of the film: "It will make you laugh, cry and eat your hats. The laughter comes from it being a comedy. The tears are going to come from the laughs. And the hat-eating is optional."

The plot centres on a group of pampered actors with huge egos who sign up to star in an action film about the Vietnam War.

The director instead drops them into a real danger zone, with only their fake weapons for protection.

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