Invisi-ghoul

Invisighoul is the sixth Mini-game, a conveyor-belt level unlocked by completing Adventure Mode and three other Mini-games. 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. For some reason, although this level takes place in the Pool at night, there is no fog.The reason why is because fog is used to conceal zombies. Since they are invisible, there is no reason to conceal them.

Zombies
Note: The * indicates zombies which will not appear until you have encountered them.
 * Zombie
 * Conehead Zombie
 * Buckethead Zombie
 * Jack-in-the-Box Zombie
 * Dolphin Rider Zombie
 * Zomboni
 * Zombie Bobsled Team
 * Zombie Yeti*

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

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

Listen and look for small details for clues as to what zombies are on the screen and where they are. So don't turn off your sound, as the sound is important for identifying zombies; it is possible to tell what or where a zombie is when the projectiles hit. For example, Conehead Zombies make a dull thudding sound when hit by peas and Buckethead Zombies make a metallic clang. Peas cause a splatting explosion that lets you identify sounds. 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 Rider Zombie.

Some Zombies also alert the player they are coming by making distinctive sounds or actions. Jack-in-the-Box Zombies make music, Dolphin Rider Zombies make a distinctive cry before entering, and Zombonis have an engine noise and leave an ice trail. In addition, if a zombie enters the pool, there will be a small splash, which alerts the player there is a zombie entering the pool.

Even though the zombies are invisible, you can see their headwears (if they have one) and arms come off when they are have reached their corresponding health, and their heads fall off when they have been defeated. With the use of the Ice-shroom, ice forms around the zombies' feet, making you aware of their location, but also giving you time to set up defenses in certain lanes. This does not apply to Zombies in the pool, but does apply to zombies on land.

Trivia

 * This Mini-game takes place in the Pool in the nighttime, but there is no fog.
 * Invisighoul might be named after the enemy Invisighoul from the Yoshi series that carry objects which you can eat.
 * Invisighoul is a pun on the word "invisible".
 * It is only possible to kill the Zomboni safely with a Squash.