The amount of character that has appeared in Planetary Moe is as much as the stars in the sky, so the characters are separated into various categories.
- The Planets note Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
- The Not-Quite Planets note Pluto, Ceres, Makemake, Haumea, Eris
- The Moons and other Bodies note Selene/Luna, Phobos & Deimos, Io, Europa, Ganymede, Callisto, Titan
- The Stars note Sol/Sun, Alpha Centauri, VY Canis Majoris, Summer Triangle, Sirius A & B, Bellatrix, Blue Strangler, and more
- The Cosmos note The Black Hole/Sagittarius A, Lady Milky Way, Old Man Universe
