From what I could tell of vehicles or people in front of the camera they were only there for a single frame. (Which would be correct if he was filming individual frames of his animation.) The eye and brain just plays a trick on you. If anyone wants to check closer go back to his site and download the AVI and step thru it... Personally, I don't care enough
The movie makes me think if Bill Plympton was born a graffiti artist... Also reminded me of this guys floor art...
http://users.skynet.be/J.Beever/pave.htm
-MJ