The human hand is one of the most complicated and delicate pieces of machinery there is. Millions upon millions of tiny parts all work together to make the hand work. We can do most anything with our hands, and certainly couldn’t do a lot without them. Yet what would we do if our hands gained sentience?
It’s not unprecedented, of course. What are sock puppets but hands with masks on? The Addams family had a pet hand that flew around and did some crazy stuff. In Harry Potter, a magical hand strangled Wormtail for incompetence, and Eric Cartman’s hand played a pretty convincing Jennifer Lopez for a time.