But his latest may be a step too far - as the actor dons make-up to play a rather convincing looking black man in a new Hollywood film starring comic actor Ben Stiller.

In a still from film Tropic Thunder, Downey Jnr is sandwiched between Ben Stiller, and a blonde Jack Black.

Downey Jr plays a worthy Oscar-winning actor taking on a role originally written for a black actor, and rather than re-write the part, he goes method.

Clearing anticipating a backlash, Downey Jr told a US magazine: "If it's done right, it could be the type of role you called Peter Sellers to do 35 years ago. If you don't do it right, we're going to hell."

The cast also includes Steve Coogan, Nick Nolte and cameos from Tom Cruise and Tobey Maguire.

Stiller said he was "trying to push it as far as you can within reality," with the intent of satirising over-the-top actors, not African-Americans.