Iron Man caught short

The director David Fincher reveals how Robert Downey Jr staged a bizarre protest during the filming of 'Zodiac'.

"He said, 'I can't work like this, I never get to go to my trailer, I never can get my shit together, I'm on my feet 14 hours a day, I'm shooting all the time. He actually left jars of urine on the set, just like over in the corner and stuff. He would go off and he would pee and then he would bring it back, and it seemed like a form of protest."

The revelation comes in the new documentary, 'Side by Side', produced by Keanu Reeves, which looks at the evolution of movies from film to digital. In the documentary, just released, Reeves interviews directors and cinematographers including Fincher, Christopher Nolan and David Lynch.

In the past directors of celluloid had to change film reels every 10 minutes, creating a tradition of endless breaks where stars spent almost as much time in their trailer as they did on set. But there's no need to stop with digital – and some pampered A-listers have had a rude awakening.

The famously eccentric Downey Jr was not taking it lying down, as Fincher reveals.