i wrote about this in one of the free will essays but i want tie downs in this idea: what if we are all trapped in our own heads, and we smile through our teeth but it is not us smiling, somewhere something inside me (me) is and not controlling anything. and my avatar of a body fakes it's emotions. good semi-illustration is the film Get Out. only there is no other user controlling me. it's simply automatic.
terrifying because determinism may point to this idea. but it also suggests dualism.