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