Back when his books were my textbooks he still had email. I would have emailed him if I had known it was a limited time offer. Now I guess I missed my chance.
Interesting. Sort of like what were called 'hanging miniatures,' or even matte paintings on glass. As long as the camera doesn't move, but only rotates about itself (pans or tilts) or zooms with a zoom lens that frog will appear locked to the background. If the camera moves, however, the close frog will appear to slip with respect to the more distant background and the illusion will be lost. That's how the camera was able to tilt up and down to follow Butch Cassidy and the Sundance Kid as they jumped off that high cliff, even though the cliff was a painting on glass close to the camera and the jump location was actually around Malibu.
https://www.youtube.com/watch?v=_am1ydf8QRA&feature=kp
They look like they are having a lot of fun.