Prince Theo (ティオ) is the main character in Nobita and the Legend of the Sun King. He's a hardhearted, as well as slightly tsundere person who wants to know how to be the great king.
Theo is identical with Nobita with exception his hairstyle, his clothing and not wear glasses.
Theo can be described as completely opposite of Nobita. He is harsh, reckless, somewhat selfish and has no caring personality at the start, as strength the only thing he believed that would lead him to become a successful king. He never even acknowledged (or more-like, doesn't even care of) Kuku's loyalty and love towards him. When he met Nobita however, he started learning about friendship and caring for other people. By the end of the movie he has become a kind and caring king and he seems to accept Kuku's feelings.
- The difference between Theo and Nobita is that they are opposite and personality.
- Apparently in the Cantonese dub, Theo and Nobita are shared same voice actor (Doris Lo).