This states the famous Jade Emperor said the order of the animals in the Chinese zodiac would be decided by the position in which they arrived at his party.
The rat tricked the ox into giving him a ride and then, just as they arrived at the finish line, the rat jumped down and landed ahead of the ox, coming first.
The rat is also associated with the Earthly Branch and the midnight hours.
In terms of yin and yang the rat is yang and signifies the start of a new day.
In Chinese culture, rats are seen as a sign of wealth and excess and due to their rate of reproduction, married couples often prayed to them for children.