The cat is the fourth animal symbol in the 12-year cycle of the Vietnamese zodiac, taking place of the Rabbit in the Chinese zodiac. As such, the traits associated with the Rabbit are attributed to the cat. Cats are in conflict with the Rat.
Legends relating to the order of the Chinese zodiac often include stories as to why the cat was not included among the twelve. Because the Rat tricked the cat into missing the banquet with the Jade Emperor, the cat was not included and wasn't aware that the banquet was going on and was not given a year, thus began the antipathy between cats and Rats. It is possible domesticated cats had not proliferated through China at the zodiac's induction.
There have been various explanations of why the Vietnamese, unlike all other countries who follow the Sino lunar calendar, have the cat instead of the Rabbit as a zodiac animal. One explanation is that the ancient word for Rabbit (Mao) sounds like cat (Mao).