What if a rocky planet didn't have a core? That can't happen, can it? It should differentiate... well, there might be a set of circumstances under which that might happen. If it does, they're going to be a bit strange. As to how they might be weird. They might deform more due to rotation and gravitational distribution; they might have an unstable or no magnetic field, and the minerals on their surface would definitely be exotic. Link: https://www.pnas.org/doi/10.1073/pnas.2615884123 #Exoplanets #Worldbuilding