OK, that's a cool trick.
Black Magic Fuckery
Videos of anything that clearly has no explanation other than no good black magic voodoo fuckery
Pretty neat! Based on how it's one foot stays down and slides around, I'd guess there's a few magnet tricks going on. Maybe a magnet behind the canvas allows for precise movement? Could also be special ink that shows up when painted on with water or another chemical, so the drawing is pre-made and then just selectively revealed. But... the brushing looks pretty real! So yeah, I think my answer is "lots of magnets." Great trick!
I think the answer is that it's a hand puppet. It's leg doesn't leave the table because there is an arm up it. The whole set-up to make that work is very impressive.
Pfft. This is just wee Jimmy Krankie doing some painting.
It's obvious now you've explained it.