Practically impossible photos. That's what people call for these kind of photography technique.
And you need some who is not so shy to try this out in a public place. It keeps the amusement, make people to stare again and again to make sure what they see is correct.
Here you need a plan. You need to visualize the image in your mind before you click. Minimum two images of the same frames. One with subject and the other one without subject. Then you merge it together and get rid of the unwanted portions. Take care of the shadows and reflections.