Ben Stiller: 'Downey Jr is a genius'

Ben Stiller has described his Tropic Thunder co-star Robert Downey Jr. as a "genius".

The comedian admitted that he began mimicking Downey Jr. during filming, hoping that some of the actor's skills would rub off on him.

"I started trying to copy him," he told Playboy. "It was like, 'Wow, this guy's a genius - maybe if I do what he does, I'll be a genius too!'"

He continued: "If he had spun around and thrown oat bran at the moon, I'd have run out, bought some oat bran and started spinning.

"I want to look like I'm as big a genius as he is."

Tropic Thunder, which also stars Jack Black, Steve Coogan, Tom Cruise and Nick Nolte, is released in September.