Error is a deep introvert that doesn't talk or trust much more people than his friend Nightmare Sans.
He can be cruel and kill you, but is rather left alone without any need to fight. He's mostly too tired for that from the lack of sleep.
Error has hapophobia: the fear of being touched. He basically glitches out when he is being touched by someone, but it can get better if you are a close person to him.
He has a pair of glasses, but never wears them to avoid being called names and look weak.