The rat was given the task of inviting the animals to report to the Jade Emperor for a banquet to be selected for the zodiac signs. There were fourteen animals that he was told he must invite: the ox, the tiger, the dragon, the snake, the horse, the sheep, the monkey, the rooster, the dog, the boar, the cat, and the wolf.
those of the sohma family are cursed by the zodiac. select members of the family - the juunishi - become their true form when hugged by a member of the opposite sex..
but it's not only the zodiac members who are affected. it's everyone who was ever invited to attend the banquet.