Instructions
Complete the Adventure game mode. Once the Adventure mode is complete, it begins again starting with Level 1-1, offering new twists on old stages.
Play Adventure mode again until you reach Level 4-10.
Defend your house until the last wave of zombies approaches, indicated by the message that appears on screen when this occurs. In the wave of zombies is a Yeti Zombie. You do not need to defeat him to add him to your Zombie Almanac; seeing him is enough.