Brian Now said:
Please try to explain! I still don't completely get it. I can see in the video that the kid's torso looks unnaturally long. I also think I see something black behind the "legs" at one point. But that's all the fakery I have picked out so far.
Notice how he walks all stiff? Those are dummy legs and he is hiding his real ones behind it. You can catch a glimpse of this in the vid.
Watch him when he floats. He is moving his shirt to the side to give the appearance he is cutt in half. He's relying on the curtain and dummy legs to shield the rest of his body from sight.
Here's a similar concept and trick. Get some shoes. Place them on the floor, then stick your knees in them. Anyone from a certain front angle will NOT see your shins behind your upper legs and you'll look like dorf/Tim Conway's midget character.
If there is a specific part you are stumped on regarding the boy's version of David C's trick, ask. I can explain all of that one. I haven't rewatched all of Copperfield again, I do recall he went out to the side more and wasn't directly behind the dummy legs. However, it looked like something like a blue screen and editing occured. I don't know for sure though, since I wasn't in the audience.
Oh, for the sitting in the chair part in the boy's vid, find a stool, sit on it, then move your legs to the side while facing forward. That is what he is doing, meanwhile hiding his legs behind the dummy. If you'll notice, he is very careful to hold his shirt down when sitting to hide his lap. Also, at times you can see he is really wearing black pants.
If still lost, I have a webcam, and I can try to take some images of myself demonstrating it later. I've never uploaded any images here yet, but think I can figure out how maybe.