Call of Duty: Black Ops Rezurrection trailer sort of explains space-zombie outbreak
They took zombies into space, they put zombies on leashes, they blasted them with experimental weapons, but putting a zombie on a treadmill was one step too far. The new moonbase map that comes as part of the new Black Ops Rezurrection pack looks like it could be the most interesting of the lot. The reduced gravity means dead zombies drift comically into the sky when dispatched, and the whole space suits + machine guns combo is a good one. Reminds me of the underplayed space shooter, Shattered Horizon.