At about 1:38 or 1:39 into the video, Walken does this cartwheel thing and jumps sideways. He did it, right? Well, he probably didn't do it really, it was a double doing it for him. Anyway, the fact that he did not do the cartwheel is even more apparent if you watch the bottom of the screen while the double is doing the amazing trick! Watch the bottom very carefully, and for a little while, a second and a half maybe, you can see MR. Walken's back bobbing up and down! After the double is done, all Christopher has to do is stand up and continue on dancin. :)