Cryptozombologist

Difficulty: Medium-Hard

This Achievement is pretty hard. It's unlocked by encountering the Zombie Yeti, which is found in level 4-10 after beating Adventure Mode for the first time. The Zombie Yeti will appear every time the player plays level 4-10, as well as in some random levels and some specific mini-games listed at their own page (it will only appear in minigames after you encounter it on level 4-10). You don't need to kill it to obtain the achievement. It will give 5 diamonds when first killed and 4 after that, but will run away after a short time on the lawn so make sure you kill it.

Trivia

 * The word "Cryptozombologist" comes from the Greek kryptos, "hidden, secret", and -logia, "study".
 * This achievement is called Zombologist in the iPod Touch/iPhone/iPad version, and Game of the Year version for the PC and Mac (excluding the Steam versions).
 * The image from the iPad looks different, as it is not blacked out.
 * It is one of the few achievements involving a zombie that does not involve killing a certain zombie.
 * In Game of The Year Edition, it says "Discover the Yeti Zombie" instead of "The Top Secret Zombie".
 * Technically, this is because it's a completely different achievement; it's called Zombologist instead of Cryptozombologist.
 * It may be hard to get because 4-10 does not have any instant kills.