July 2nd 2012 came the first "event" oriented minor game update. For the few days surrounding the 4th of July there are more zombies and even better more exploding zombies showing up at your gate. The supply boxes and coins also shoot twice as high into the air (like fireworks...hint hint). Little things like this really take games to a higher level. So let's hope lots more stuff like this come in between major updates.
I've seen up to as many as 8 of the red zombies on the screen at once. Messy...messy...messy.