The Denizen plugin is an expansion of the Citizens plugin that allows for extra actions, commands, and poses for NPCs. With Denizen you can mirror the NPC's skin to share the skin of whoever is looking at it, you can make the NPC sit, stand, sleep, crouch, and fish, and more. I haven't found a way to perform any of these actions with Skript or the current Citizens plugin, so Denizen would really help out.