The King's Speech star will give voice to the cuddly character in a new movie based on the books by English author Michael Bond, about a bear from Peru who is adopted by a family who find him lost and alone at the London railway station which gave him his name.
Firth will reunite with his The Railway Man co-star Nicole Kidman, who plays the movie's villain, and Downton Abbey's Hugh Bonneville as head of the family which adopts Paddington.
He tells Britain's Daily Mail, "Paddington will be computer generated, and I will speak his lines with, I suspect, a slight Peruvian flavour. Every other character in the film will be real, live, human beings. But the idea is that Paddington will have something of me in his Dna because I'm going to do some sessions wearing one of those helmets with cameras to capture my face muscles, and all that data will somehow be incorporated into Paddington. Then they'll use motion- capture equipment on someone more bear-size than me to do all the full body, bear stuff."
Firth's co-star Kidman insists she was thrilled to have been offered the chance to make a film about the famous bear as she has been a fan of the stories since childhood, adding, "I just had to do the bear film. My agent called and said: 'We've got this offer from London for you to be in a film about a Paddington Bear.' And I said: 'You mean the Paddington Bear?' I was read the stories when I was little and I grew up with Paddington. I know all about his adventures and what mischief he got up to."
Filming will kick off in London in the autumn (13).