(Un-)Stable Stool - (Un-)Stable is a stool which at first sight looks extremely unstable, because it is an awkward height and the legs come down square to the seat, making it look like it will topple over as soon as it is used.
When one sits on it, it initially reacts as expected: the legs splay out, and the seat slips down towards the ground. Not only is the feeling of instability confirmed, but it is enhanced even more.
But after this initial moment, the legs lock in a splayed position, so that the stool actually becomes extremely stable, countering our expectations about it and creating a pleasant surprise: the stool is actually very usable.