Dragon Ball is a long running Japanese TV series that has extended through
3 separate incarnations. The first was titled Dragon Ball and was sort
of a coming of age stories of Goku, a boy with a tail. In this series,
it recounts his fighting exploits and his change from young innocent (but
extremely powerful boy) to extremely powerful (but not so intelligent)
mature man.
The second series was titled Dragon Ball Z and extended for around 7 seasons
and a number of movies. Goku finds out that he is from outer space and
must protect earth from a number of threats from outer space (whether they
be relatives, robots from the future, or a being composed of his own cels).
The cast grows significantly with the introduction of Vegitia. He is at
first a villain, but later will become a grudging ally of Goku and Gohan
(Goku's son) and marry Bulma (the first female that Goku ever met). Vegita's
son, Trunks, will play several significant roles in this series and is
one of the most popular characters to have came out of this series.
The third series was titled Dragon Ball GT and revolved around the finding
of seven special dragon balls, which if not re-found will cause the end
of the universe. Goku in this series is returned to a young boy for a while
by a mis-spoken wish and includes a number of the children of the Dragon
Ball Z cast in addition to many of those who were already present in Dragon
Ball Z.