User blog comment:Pigman0439/Which Mob Monster is Your Favorite?/@comment-25120690-20140701193206/@comment-4752762-20140701195811

Fun fact: There should be no difference between a Witch's biology, and a Villager's biology (except the nose and the mouth; maybe the skin has a little difference as well).

But, zombies attack villagers, but not witches. Why?

Villagers hit by lighting turn into witches.

My teory is that witches are actually 'testificate (human)-like monsters'. They look normal, but no difference between them and zombies, skeles. They of course are smarter. They can make potions, have a possible secret acces to the nether and their huts. They probably stay in-doors during day (you can find witches inside the huts), and come out at night to find targets/victims and potion ingredients.