These are Ben's Squares.

The squares all start at the bottom. Then one at a time, they go out and do their dance and come back to the fence. And when they all are back at the fence, they go home. Then, they go two at a time, and dance together, and when everybody has gone two at a time, they can go home. Then three at a time, then four at a time, then five at a time, then not six! And then, one at a time again.... and the whole thing again, and then twice with all six.