Unlock the Punk hero.
Defeat the Horned Boss.
Unlock the Princess heroine.
Unlock the Pirate hero.
Buy the Shotgun gun.
Unlock the Ninja hero.
Find a Crystal Skull.
Unlock the Mime hero.
Unlock the Hippie hero.
Kill a Shredder enemy.
Buy the TwinShot gun.
Kill a Bomber enemy.
Kill a Track Shooter enemy.
Buy the Plasma Pistol gun.
Kill a Hopper enemy.
Kill a Red Horned enemy.
Defeat the Turtle Boss.
Unlock the General hero.
Unlock the Dino hero.
Kill a BrainWorm enemy.
Kill a Zombie Turtle enemy.
Kill a Worm enemy.
Buy the SMG gun.
Defeat the Muscled Boss.
Unlock the Professor hero.
Unlock the Hobo hero.
Buy the Magnum gun.
Unlock the Agent hero.
Unlock the Trucker hero.
Kill a Zombie Runner enemy.
Unlock the Lunatic hero.
Unlock the Gentleman hero.
Kill a Flyer enemy.
Kill a Zombie Shooter enemy.
Unlock the Cop hero.
Kill a Zombie enemy.