Black, who makes his directorial debut with murder mystery KISS KISS BANG BANG, was wary of working with troubled CHAPLIN star Downey Jr, and "potentially difficult" Batman Forever actor Kilmer, but soon realised there was nothing to worry about.
He says, "Downey did drugs, and now he does not. He knows that and, having worked with him, I know that.
"And Kilmer was always presented to me as potentially difficult, but on the set he was fun, he kept everybody laughing.
"He has this real arch, deadpan sense of humour - he's hard to read sometimes because he's dry, but he's funny."