Robert Downey Jr to play talking dog

London: Robert Downey Jr is all set to lend his voice to the character of a genius dog in a new animated film.

The `Sherlock Holmes` has signed to star as cartoon character Mr Peabody in the big screen adaptation of the `Rocky and Bullwinkle Show`, Contactmusic reported.

The animated feature will be a tale of Mr Peabody`s adventures along with his pet boy Sherman as he travels through time using his WABAC time machine, learning about history`s greatest figures.

Director Rob Minkoff said the movie will also focus on Mr Peabody`s origins. "Mr Peabody is this genetic anomaly. He does have brothers and sisters, all of them non-speaking, no super-smart dogs. He`s an outcast, but has overcome it by being so great at so many things."

The role of Sherman has not yet been cast while `The Simpsons` veterans Jeffrey Ventimilia and Joshua Sternin are writing the script.

Downey Jr will soon begin recording his voiceover work for the as yet untitled 3-D animation movie with an expected release date of 2014.