~The Rabbit has been Removed from the game.~
The rabbit is a companion for your horses. When they play together, it'll give you all kinds of advantages:
Dressage bonus: +3
Until 18 months: A gain in Genetic Potential for each hour of play
From 20 months until 25 years old: Winnings for one hour of play: 6 Equus
Could be bought at the store for 1000 equus.