[Lirange]

It's from fruits basket.
I copyed that, so it isnt very good, i'll try to put it in my words.

So long ago, god invited all the animals to the banquet the next day. All the animals were excited. The rat decided to play a trick on the cat. He said the banquet isnt tomorrow, but that day after tomorrow. The cat thanked the mouse and they part ways. On the day of the banquet 12animals came. The rat rode on the ox, and once they were at the entrance, the rat jumped off it and was the first one. The next day the cat arrived, and learned the banquet was yesterday. He was sad, and is mad at the cat.

You can always read fruits basket for the better telling of it, its in the first chapter or two. So that is why the cat hates the mice. And that is why the mice is first on the zodiac. And that is why the cat isn't included in the zodiac.