The latest snapshot (The latest Minecraft snapshot
) has added two new mobs - the bat and the witch.
The bat is small, black and cute. It flies around and is neutral to players. I don't know yet where it spawns but I imagine in dark places.
The witch is basically a villager dressed in purple with a wart on its nose and a witchy hat on its head. It is hostile to players in survival. It attacks by throwing potions. Its normal attack is poison but I have also been hit by slowness and weakness.
I'll add more information as it comes to hand.