In your explanation of the Great Wall illusion by Copperfield, you fail to explain one thing: where did the assistant go? I think it is much more likely that there is no assistant, and Copperfield himself casts the shadow.  He then slips down into a hidden compartment in the box. Note that when the camera moves to the other side of the wall, there is no box.  The box, with Copperfield inside, is simply moved off-camera to the other side of the wall. Look carefully at the bars under the box - as the box rotates as they are moving it away, the perspective gets a bit weird - I think those are mirrors.

Our reply: Thank you for your feedback. We will put a thread about this on the forum and let the users decide =)