stupid jokes from my friend

My friend is quite a talkative person.One day as usual he talk all the time in front of his elder sister.His sister feel that he is annoying her to continue to complete certain things.His sister shout at him "hey,silent please".My friend stop moving his mouth and this time he started to move is body like a machine.His sister feel freak with his movement and ask him what is he doing.My friend answered his sister "just now you ask me to stop talking and now vibrate".His sister have no idea about him.