Zombies.....could it REALLY happen?

Moneypenny • Leaving Glow was the best thing I did!
After seeing some comments on other posts (people comment YES it can happen), I am curious if people really believe zombies are a *real* possibility.
Do you really "believe" it can happen OR are you just a huge fan of The Walking Dead and the idea of it scares the pee out of you?!
IF you do believe it's possible ....why? 
Do you feel there is actual scientific proof or some other type of proof you can share with me!  
I'm curious what others REALLY think about this!