He is well known for his amazing tricks with human partner Ashleigh, but once it was announced that Pudsey would be breaking into the movies, he needed a voice, and BGT judge Walliams seemed the obvious fit.
Walliams said: "Getting into character as Pudsey, it's mainly about watching Pudsey on the screen and trying to capture his personality.
"He has got a very strong personality, he's got an under bite as well and he sort of knocks his head from side to side trying to understand what people are saying to him.
"And so I just try to get that sense of eagerness and optimism."
"I think it's going to be such a surprise to a lot of people," added Ashleigh.
"I don't think people would expect (David) to be playing (Pudsey) but I think he is going to do a brilliant job."
Since winning BGT in 2012, Ashleigh and Pudsey have travelled the world and met a host of famous faces, all while showcasing Pudsey's exceptional talents.
His first film sees the talented pooch befriend a group of children in a sleepy English village, as he helps them outsmart an evil landlord.