I saw some pictures like this the other day on Flickr and I couldn’t wait to try it out myself. Luckily, Paige is usually a willing subject. Here she is relaxing in the chair and watching the baby:
This time she’s sitting on the couch and standing up and smiling:
These are actually pretty easy to do with a digital camera and a few minutes of editing. First, take two pictures of your subject without moving the camera (a tripod really helps here). Then layer one image on top of the other in something like PhotoShop or The GIMP. Finally, erase the area in the top layer so that the image of your subject shows through from the bottom.