The Witchsweeper Game
In a faraway land there lives a large family of witches who like to play tricks on the animals that live nearby. One of their tricks is to change the animals into toads. Needless to say, the animals are not very happy about this, even though the witches' magic only lasts for a short time.
A witch's magic is not greatly powerful, and can only affect an animal next to the witch (horizontally, vertically, or diagonally). Not only that, but some animals require too much magic for a single witch.
One witch can change a cat into a toad, but a dog is more difficult, so she has to call for another witch to help her. Thus, a cat will be surrounded by one (and only one) witch, whereas a dog will be surrounded by two witches. There are also some horses in the neighborhood; they are more difficult for the witches, and it takes three of them surrounding a horse. What about a cow? Four witches.
You are the good fairy who has come to help the animals and protect them from the witches' magic with your powerful magic fairy dust.
There are also rabbits, which are too smart - or just too fast - for the witches, who can never get next to a rabbit. The rabbits are your friends and will help you. If you click on a rabbit, it will share your magic fairy dust with all the animals surrounding it, thereby protecting them. And if any of those are rabbits, they in turn will do the same. In this way, a rabbit will often help you to protect many animals.