All creatures were invited to a gathering for Buddha's leaving
This is the Year of the Snake according the Chinese zodiac. The Chinese zodiac has a 12-year cycle. It is represented by 12 animals - the rat, ox, tiger, rabbit, dragon, snake, horse, goat (or sheep), monkey, rooster, dog and pig.
Although the origin of the Chinese zodiac is unclear, there are two legends about how the animals were chosen.
One legend has it that before Buddha's final departure, all the animals on Earth were invited to a gathering. However, only 12 showed up. To honour the 12, Buddha named a year after each in the order of their arrival.
The other legend says that the emperor of heaven, the Jade Emperor, held a race on his birthday. The 12 fastest animals in the race would be chosen to represent the 12 years of the zodiac. Animals had to cross a river to reach a designated shore.
Originally, the rat and the cat were good friends. But both being poor swimmers, they asked the powerful swimmer, the ox, for help in crossing the river. The ox agreed to give them a ride. However, during the crossing, the rat was afraid its buddy, the cat, would win, so it pushed the cat into the river. The cat did not win a place in the race. And that is why cats hate rats today.
Before the ox arrived, the rat jumped ashore and won the race. The ox came in second.