this category is dedicated to those sneaky little bastards known as hidden categories, which stay hidden for a reason. You see, a hidden category won't appear alongside the other categories, so unless you fiddled with your preferences, you shouldn't be able to find this page. And woe those who do... *gun clicking*
To spawn such sneaky categories, all you need to do is to just add
__HIDDENCAT__ on the category, and voíla!