I recently discovered New York street artist, Joshua Allen Harris, while in Indonesia. Joshua creates inflatable puppet-sculptures that get life breathed into them by the air on the streets getting pumped up by the subway below. He uses old shopping bags to create these amaising animation.
His Loch Ness Monsteris probably the largest creation he has built to date - check it out here. There are quite a few of his short creature films, which you can watch on Joshua's website here.