I have been reading on this glitch/hack/easter egg. And what i have been able to find is that you have to shoot the heads off of every manikin in the level and once you do so a surprise happens the results vary from a nuketown zombie mode, or the fallout shelter opens, or other random things. I'm on ps3 right now with two other people trying to figure this out. My psn is DesmondDarosa send me a message if you are willing to to try this out or give me some info on it. Thanks.