Playing Catch With a Human!
Today we use spacing and posing and looping to create the illusion of volleying a human back and forth. Stop motion animation is kind of funny in that we don't move when a picture is taken. The process is: move to a new position. Stop. Take a picture. Move to a new position. Stop. Repeat.
Do the math based on 15 pictures per second, and you can invent almost anything you can imagine. Pose, move, pose. etc. Stopping and moving. Stop motion.
Makes sense right?