Screen Space vs. Physics

It's always interesting when something works in animation that doesn't abide by the laws physics. Here's an example from Chuck Jones' "Dover Boys of Pimento University".

The boys are tiptoeing over from one place to another.
First Frame

Second Frame

Third

Fourth

The strange thing is that between drawings 2 and 3 the character actually moves up in screen space. But that shouldn't happen. His feet aren't touching the ground yet. There's nothing to propel his body upward, and gravity should still be pushing it down. But if his body kept moving down there would be too much of a spacing difference between drawing 3 and 4. So the animator decided he needed to defy the laws of gravity to make the walk work smoothly. And it does. Watching the cartoon, the walk is funny, and there doesn't seem to be anything wrong with it.