Could a zombie apocalypse really ever happen? Well, sure it could...if there were really zombies. But since, at least at this time, there is no such thing as zombies, the chance of a zombie apocalpse taking place is next to none. In the event that zombie surfaced and began to walk the earth, an end of the earth as it is known would surely take place. That would be considered an apocalypse.
In fact, odds are that it would be inevitable for the world to end. It would be easy to spread through the same ways zombies would spread it, through water, air, and sexual contact. So that aspect of it is not far fetched. Many think that the end of life on earth will end in a pandemic or similar situation so minus the zombies, that's pretty close to the scenario.