Goku

Goku is a Saiyan born on Planet Vegeta (His Saiyan Name is kakarot), like many other Saiyans. He was sent on a escape pod by his father Bardock, him thinking that the planet would get destroyed. He lands on planet Earth, falls and hits his head, which causes a malfunction in his brain, making the original plans to destroy earth wiped, becoming the go-happy Goku we know today.