Before WOTLK, Blizzard set events with zombies everywhere in Azeroth. I made a few rush of it, and decided to edit it on a song by Wednesday 13 called "I walked with a zombie".
Basically, if you were bitten by a zombie, you would become one a few minutes after the bite. Then you could talk in a language only understood by other zombie players. Non zombie players would see you say : BRAIIIIIINSSS ..... !
You could also explode, by using a suicidal spell, and that would turn everybody around as zombies.
This was made on august 2009, I am uploading it again, as it was previously hosted on Gametube that shut down.