Invisi-ghoul

Invisighoul is the sixth mini game, a conveyor belt level unlocked by completing Adventure Mode and three other minigames. It takes place in the Pool area at night with all of the zombies invisible. Items from the zombies, such as ice trails from Zombonis and buckets falling off of zombies, will be visible for a short time.

Zombies

 * Zombie
 * Conehead Zombie
 * Buckethead Zombie
 * Jack-in-the-Box Zombie
 * Dolphin Rider Zombie
 * Zomboni
 * Zombie Bobsled Team

Strategy
The plants provided are Peashooters, Lily Pads, Kernel-pults, Ice-shrooms, Wall-nuts, and Squash.

The Rake is highly suggested on this level, as it provides you with time to set up your defenses so the you can have weapons in every lane to protect from possible zombies.

Ice-shrooms are also very helpful, as they reveal the wherebouts of all the frozen zombies (excluding those in the water).

Listen and look for small details for clues as to what zombies are on the screen and where they are: Conehead Zombies make a dull thudding sound when hit by peas, Buckethead Zombies make a metallic clang, Jack-in-the-Box Zombies make music, Dolphin Zombies make a distinctive cry before entering, and Zombonis leave an ice trail.

It is also possible to tell what a zombie is by where the projectiles hit it. For example, if a pea hits a zombie near the beginning of the pool, and the next pea hits much farther into the row, the zombie must be a fast zombie, in this case a Dolphin Zombie.Note that Dolphin Zombies make a distinctive sound before entering.

In addition, if a zombie enters the pool, there is a small splash, which does not help identify the zombie but can alert the player as to the fact that there is a zombie there.