They’re us, in other words. And like us, they’re not all bad. The paradox at the heart of “Wall-E” is that the drive to invent new things and improve the old ones — to buy and sell and make and collect — creates the potential for disaster and also the possible path away from it. Or, put another way, some of the same impulses that fill the world of “Wall-E” — our world — with junk can also fill it with art.