When we first saw that Netflix had 'hidden categories' we thought they'd just be a couple of options like 'Spirituality Documentaries' or 'Satanic Stories', not a list of hundreds of categories that are genuinely useful. (Although both the previously mentioned categories are actually available.
Whenever you go into a category on the Netflix website you get a URL that looks something likes this www.netflix.com/browse/genre/6839 - if you play around with the 4 numbers at the end of the URL you can find some hidden gems.
This site lists all the numbers that have currently been found. The amount of categories are crazy.