Yuhuang Dadi (the Emperor of Heaven) invited all the animals on earth to join the celebration of his birthday.But of all the animals only 12 showed up.Those were:The Rat,The Ox,The Tiger,The Rabbit,The Dragon,The Snake,The Horse,The Goat,The Monkey,The Rooster,The Dog and The Pig.For their effort,the Emperor honoured each animal with a year of its own in order of their appearance.He also decided that those who are born in the year of the animal will assume the characteristics and the nature of that animal.In fact the Ox was first,but the rat sitting on the Ox's head,bet with the Ox,if they were walking around the holy grounds,it will emerge as the bigger animal.The Ox agreed.As they were walking around they heard all the other animals and even the fairies say:"What a big and disgusting looking rat!"."You see",said the rat,"every being in this holy grounds sees me as the bigger animal." So without any further arguments the tolerant Ox carried on.This is one of the stories how it came to that the rat is the first in the chinese zodiac.