What are the requirments to turn into a zombie in sims 2 free time?

I have been able to turn into a zombie once from the genie lamp and i have tried to do it a couple more times and the person that got who came back to life ended up the as a totally okay sim. I just wanted now what has to happen in order to make the person a zombie? I do not have university installed just Open for Business, Pets, and Free time.