Samurai Jack

Samurai Jack tells the story of a young prince (Jack) from Feudal Japan whose father's empire is destroyed by the shape shifting demon Aku. As a child, the prince escapes destruction and travels the world training his mind and his body for years until he reaches adulthood, becoming a legendary samurai. After taking his father's magic katana, he challenges Aku to a duel and defeats the demon. However, before the prince can deal the killing blow, Aku creates a time portal and sends his opponent into the distant future, anticipating that he would be able to amass sufficient power to deal with the samurai later. He arrives in a dystopian, futuristic Earth ruled by Aku and filled with his robot minions and a large number of alien immigrant races of various appearances. The first people he encounters in the future call him "Jack" as a form of slang, which he adopts as his name (his true given name is never mentioned in the series).