How to: Make a Movie with Digital Stills

"Don't get the idea that I do any fancy z-axis 3-D virtual camera math or programming! I just combine elements from a couple of pictures, separate things into layers in Photoshop, replace backgrounds and then wiggle 'em around in After Effects. All the parallax scrolling and zooming are figured out as I go shot by shot. I think of myself as primarily a live action guy so I just adjust the scale, position, and blur keyframes until they look right to my eye."

So that's how he did it.