Dragon Ball Z (from Dragon Ball Wiki)
Dragon Ball Z follows the adventures of the adult Goku who, along with his companions, defends the earth against an assortment of villains ranging from intergalactic space fighters and conquerors, unnaturally powerful androids and near indestructible magical creatures. While the original Dragon Ball anime followed Goku through childhood into adulthood, Dragon Ball Z is a continuation of his adulthood life, but at the same time parallels the maturation of his son, Gohan, as well as other characters from Dragon Ball and more. The separation between the series is also significant as the latter series takes on a more dramatic and serious tone. The anime also features characters, situations and back-stories not present in the original manga.

Son Goku, born Kakarot, is a Saiyan raised on Earth and the main protagonist of the Dragon Ball series. He is the secondborn, as well as youngest child and son of Bardock and Gine, the husband of Chi-Chi, and the father of Gohan and Goten. Originally sent to Earth by his parents as an infant, Kakarot was adopted by Grandpa Gohan and renamed Son Goku. A head injury at an early age altered Goku's memory, ridding him of his initial destructive nature and allowing him to grow up to become one of Earth's greatest defenders. Goku constantly strives and trains to be the greatest warrior possible, which has kept the Earth and the universe safe from destruction multiple times.