You employed 20 construction zombies.
You built five blockades with super awesome finish in a row.
You won all gold medals in all singleplayer levels.
You completed all single player levels.
You killed three zombies with one melee attack.
You built every trap and a wood blockade in one level.
You killed 20 zombies with a single bomb trap.
You searched four cacti in a row while playing Mike.
Ten infected zombies danced at the same time.
You played five minutes in darkness.
You activated the Jukebox and make a zombie dance.
You blocked all the doors and windows in one level.