I remember a while back I was in Electronics Boutique (a Gaming store), and I noticed a game for Playstation called "Magic Monkey." I picked it up and read the little summary on the back, and it sounded a lot like the story from Dragonball.

Well, I looked it up, and both that game, and Dragonball were based off of an old Chinese Myth. It seems the myth is based off of a monkey (also named Goku), a pig (Oolong), an Ox (Ox King), and a character resembling Master Roshi.

The story is basically about a Shaolin monk who has three pupils - a monkey, a pig, and an ox. The monkey, who was the Monkey King, if I'm not mistaken, had many powers, including the ability to cause destruction with his magical staff. He had the power to make this staff grow to great lengths, or shink to hide from enemys (power pole). The Nimbus cloud also comes from somewhere in this myth.

Only Dragonball was based off of this myth. If you noticed in Dragonball Z, the original characters (Oolong, Roshi, Ox King) started to appear less. Then new characters (Frieza, Androids, etc) started to appear..

That's all I know about the myth at this time. Once I learn more about it, I'll put it up here.

Other Animes relating to this myth are:

Saiyuki
Midnight Eye Goku
Alakazam the Great