Custom NPCs mod allows you to create your own little stories with custom characters inside Minecraft PE. You will be able to set up such parameters like - will it be aggressive or not, follow you or stand still, you can choose a random skin for him and particle effect. Probably the most useful functionality is for map creators - since you can make NPCs to say some text.
To create and edit NPCs you will need an item called NPC Editor (1000) - just tap with the item on a regular villager and you should be able to customize it using a special menu.