Slideshow of Chinese Zodiac Animals. There are endless variations of the folklore story explaining how the order of the animals of the zodiac were chosen.

Below is a popular telling of tale:
When it came time for the Jade Emperor in heaven to decide the order of the zodiac, he invited all the animals to participate in a race. The order of the zodiac would be decided by the order in which animals finished the race.
When the competition started, the ox was leading the pack, but the rat jumped on his back. Since the rat was so light and small, the ox did not realize that the rat was hitching a ride. As the ox approached the finish line, the rat leap off his back and was crowned as the first animal to complete the race.
After all the creatures finished the race, the order was finalized: rat, ox, tiger, rabbit, dragon, snake, horse, goat, monkey, rooster, dog, and pig.
According to legend, those born in a particular year of an animal are said to possess particular character traits associated with that animal.