Journey to the West is a novel from China thought to have been authored by Wu Cheng'en. The story is that of a monk who travels westward in search of sacred scrolls. He is given three protectors on his journey. One of these protectors however becomes more popular than the monk himself. The monkey character, Sun Wukong, becomes the inspiration for many manga and anime characters, not the least of them the similarly named Son Goku of Dragonball Z. But there have been many precursors of Son Goku. Let's see some of them.
This of course is the most popular adaptation of Sun Wukong from Journey to the West, right down to the tail and flying cloud. Yes, there was a flying cloud in the original tale. Even the name, that became Son Goku. He would evolve in Dragonball Z into a powerful alien fighter. It's likely that his alien origin was actually a retcon from this toilet-humor filled pastiche. Yet the real inspiration for Goku was the Monkey King Sun Wukong.
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One of the first science fiction adventures based on the character of Sun Wukong. Jan Cogon has the same headband, uses a staff, and rides on a spaceship that substitutes for the flying cloud that Wukong uses in the original tale. This added a unique space opera touch to the legend of the monkey king. Also, the character of Sanzo is replaced by a female, a space princess.
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The Saiyuki series features four males who are analogous to the four adventurers of Journey to the West. They are ostensibly human, although the comparisons to the originals of the Chinese tale are obvious. Their task in this anime is to prevent the awakening of a Demon King, or to fight him if it happens. In another sense, the Saiyuki characters have the feel of an Asian boyband, similar to F4.
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This is a direct retelling of the original tale itself. Goku here is Kongo, and there is more focus on other monkey characters like him. The show however was discontinued after the sixth episode, probably because the animation quality was more stop motion than fluid. see more on Monkey Magic