Unlock Brain Trophy
Type "BRAAAINS" at the cheat section in the options menu.
All you have to do is have the teddy bear in your toys toss it at your zombie and it is quickly lv.20! You get all the money you would have by leveling it up legit however you get it much faster!
Ok get a zomb box and a laser pointer. Let the zombie in the box. You have to have to box over it's head and walkig around. Get the laser pointer and play with it when your zombie is in the box. Let the laser near your the box and the zombie try to put his hands over the laser. Soon you zombie will pop out of the box and and run to get the laser. When you stop playing with the laser your zombie will walk around like it's still in the box. Have fun!