Mercury is a relatively shy planet and is easily intimidated. Due to him being the smallest planet in the Solar System, he is often the target of bullying by Venus, and occasionally, Earth. He is good-natured and careful with his words as he tries to avoid hurting the feelings of the Sun when he asks if they are friends or not. Little by little, he becomes more tolerant and assertive, standing up to both Venus and the Sun. However, there are times when Mercury would go too far when standing up.