A clip from the sci-fi comedy has been released, reported Aceshowbiz.
The two-minute clip shows the actor voicing Dennis the Dog while Pegg plays its owner.
Also starring Ben Stiller, Owen Wilson, Ben Kingsley and Rebel Wilson, the family-friendly film arrives in US theatres on December 19.
Williams committed suicide at his home in Paradise Cay, California on August 11, this year. He was 63.