This episode goes behind the scenes of Planet of the Ood

There's a trip to the Ood Sphere to witness the return of the mysterious Ood to the world of the Doctor, and a look at the various methods which go into making an Ood. Plus, how a quarry in Wales in the middle of summer gets turned into a winter wonderland, and David Tennant gets turned into an all-action hero to escape a mechanical menace. Featuring interviews with Tennant, Catherine Tate, and writer Russell T Davies.