Izzard (A Day in the Death of Joe Egg), Lumley (La Bête), Williams (Bengal Tiger at the Baghdad Zoo) and Python members John Cleese, Terry Gilliam, Eric Idle and Michael Palin will join Kate Beckinsale, Simon Pegg and Sanjeev Bhaskar.
The project, which is slated to begin shooting March 24 in London, casts Pegg as a disillusioned schoolteacher, who is given the chance to do anything he wishes from a group of aliens watching from space.
The aliens will be voiced by director Jones and his fellow Python members Cleese, Gilliam, Idle and Palin, and Williams will voice a dog named Dennis.
Ben Timlett and Bill Jones produce the film with Mike Medavoy and Chris Chesser as executive producers. Jim Acheson will design costumes, sets and the aliens.