Do you think the idea of zombies are even possible.?

I don't presonally think the idea of the classic "no heart pumping but the body is still walking around" type zombie is even scientifically possible. There's dozens of zombie movies and I'm sure there's ten times as many books about them so there's got to be some truth in there somewhere right? I once heard a theory of a type of altered mad cow disease that effects humans which sounded plausible considering a lot of us eat beef daily. I'm not talking brain-munching zombies but do you think there could be a virus that could infect humans and make them go crazy? Kind of like the rage virus in 28 days later. FYI This is a completely "just for fun" kind of question. I don't think the world will someday be run by zombies. (although a Zombieland type of world would be kinda fun ;D) Thanks Chaps