There's something odd going on in our solar system. While the planets move on nearly-circular orbits in a well-defined plane, the minor planets beyond Neptune appear to cluster together in a highly-inclined, eccentric, and tilted structure. Astronomers have invoked the presence of an additional planet (Planet 9) or even a primordial black hole in explanation. In this talk I will show that these theories may be unnecessary. In analogy with spiral arms and bars in galaxies, the collective gravity of individually small but collectively massive bodies can create such structures in the outer solar system.