From Bunni Wiki
The white cute adorable bunnies are your first and main followers through the game. While they are slow on gathering resources and need to eat a lot, bunnies are cheap to buy.
In the game, you might find several other kind of bunnies, like pirate bunnies and female bunnies (NPCs). Pirate bunnies are rare workers that you can get by shaking trees, they work faster than the foxes.
Bunni workers can be purchases for 10 wood, 10 gold from the Bunny House.