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Dragon Ball Z 
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. (from Dragon Ball Wiki)

Son Gohan (孫そん悟ご飯はん Son Gohan) is a half-breed Saiyan and one of the most prominent characters in the Dragon Ball series. He is the elder son of the series' primary protagonist Goku and his wife Chi-Chi, the older brother of Goten, the husband of Videl and father to Pan. He is named after Goku's adoptive grandfather, Gohan.

Unlike his father, Gohan is a brilliant scholar and lacks a passion for fighting, preferring to do so only when his loved ones are threatened. Nevertheless, he spends much of his life participating in the defense of Earth, often helping to turn the tides when the dormant depths of his power are unleashed.  (from Dragon Ball Wiki)