Rocks.

I remember, from some archaic science class back in my youth, that there are three different kinds of rocks: Ignatius, Sedentary and The Other Kind. (This may not be an indisputable fact, nor the technical names, but don’t mess up my memories with your scientific superiority.)


It should be noted that when a large stone jumps up and grabs your big toe, causing you to trip and fall on a gravel walkway, all three kinds of rocks laugh.