There are many legends and mythology related to Chinese zodiac and there are various versions and stories popular in different regions.
The Order of the Animals
This is the most widespread legend about Chinese zodiac. The Jade Emperor (The Emperor in Heaven in Chinese folklore) ordered that animals would be designated as calendar signs and the twelve that arrived first would be selected. At that time, the cat and the rat were good friends and neighbors. When they heard of this news, the cat said to the rat: 'We should arrive early to sign up, but I usually get up late.' The rat then promised to awaken his friend and go together. However, on the morning when he got up, he was too excited to recall his promise, and went directly to the gathering place. On the way, he encountered the tiger, ox, horse, and other animals that ran much faster. In order not to fall behind them, he thought up a good idea. He made the straightforward ox carry him on condition that he sang for the ox. At last, the ox and him arrived first. The ox was happy thinking that he would be the first sign of the years, but the rat had already slid in front, and became the first lucky animal of the Chinese zodiac. Meanwhile his neighbor the cat was too late so when it finally arrived, the selection was over. That's why other animals appear behind the little rat and why the cat hates the rat so much that every time they meet, the cat will chase and kill it.
About this simple story, there are different editions. Some say it was the Yellow Emperor who intended to select twelve guards. It is also said that cat hope rat could get there early and sign up on behalf, but rat completely forgot it or do that intentionally. Some say the animals were request to have a swimming race, or a simple race. Elephant was said to participate in the race too, but run away finally because rat got into it trunk.
