"Ceres seems to be mentally unbalanced as he behaves a lot more chaotically compared to other planets. He also tries to keep anyone away from him. This behavior might be the result of being alone for such a long time, as stated by Alvaro. Despite his seemingly psychotic nature, he behaves a bit vulnerably when others retaliate against him...he is not afraid to engage in combat with celestial bodies that are larger than him. He is also shown to be quite agile.
Ceres is revealed to be able to talk, although usually just a few words at time, often mimicking the person speaking...Makemake thinks that the reason behind the inability to talk is because he was living in seclusion, all alone in the Asteroid Belt."
- S.B.W