One of my favorite magic routines is performed by the great Tony Slydini, where he has a volunteer sit and Slydini performs some sleight of hand to make paper balls disappear in front of the volunteer. However, the sleight of hand is done in such a way that while the volunteer is unaware of what is going on, the audience can see the whole thing. So this got me thinking. Are there other magic tricks or routines that can be adjusted in such a way that when performed with a volunteer that person is unaware of what is going on while the audience is in on the gag??