A long time ago there was a group of superhumans called Saiyans who loved to fight.  But after years of destroying everything on their planet there was nothing left to do.  Then a man came along and gave them the knowledge of space travel.  So they travelled throughout the galaxy to  take over other planets. Goku, otherwise known as Kacorrot, was sent to earth.    When he landed, his ship was supposed to display a picture of the full moon to transform him into his ultimate form, a giant ape, but something went wrong and the ship crashed, making him forget his past. Then came along Gohan, an old man who adopted Goku.  After he grew up Goku married chi-chi and had a son named Gohan, named after his grandfather.