Is this alternative history of the world a possible one? And what should we make of other alleged qualitatively indiscernible possibilities? For example, is it possible for a pair of siblings to swap their actual qualitative roles—i.e., where the actually firstborn twin is born second and vice versa—but where no qualitative features of the world are altered? In a similar vein, suppose, following Black (1952), that there could be a world containing only two qualitatively indiscernible iron spheres. Are there yet other possible worlds where these spheres “swap” their respective spatial locations or are “replaced” by numerically distinct yet qualitatively indiscernible doppelgängers?