Be careful, though. Whoever is carrying the gnome will be swarmed by common infected as they "hate the gnome".

Players can now vote on which past mutation will return for an encore week. Your choices are Bleed Out, Follow the Liter and Last Gnome on Earth. The first mutation, Realism Versus, has already been made into a permanent game mode.

"The Passing" DLC is required to play mutations and vote in polls. It costs 560 MS Points ($7) on Xbox 360 and is free on PC.