I’ve known types of videos like this Tetris video, but never knew that these forms of videos were known as pixillations. Another cool video I stubbed upon recently was this Gatorade ad where they were able to trigger water droplets falling to create the shape of a human in a running pose, and stitch these poses together to make a human walk cycle.
I think it would be cool to have a capture system that would stitch together frames of people moving left to right in a walk cycle, but each frame switches to a taller person. The person could be walking in a 3Q motion that is away from the camera, so that they appear to get smaller, yet since the capture system would switch to frames of taller people, their height would stay relatively constant during the duration.
Above is a sketch of the mechanism, where each person would have a walk cycle video of them stepping on the same footholds (for alignment purposes), and in post-processing a frame frame each person can be taken to create the walk cycle.