The New Parable of the Orange
Perhaps the most famous negotiation parable involves an argument over an orange. The simplest approach was to simply cut it in half, each person getting a fair share.
But, when the negotiators began talking to each other, exchanging information about their interests, a better solution to the problem became obvious. The person wanting the orange for juice for breakfast took that part and the person wanting the rind for making marmalade took that part. Both sides ended up with more. Neither agreement is particularly inventive.
The parable of the orange becomes a story about invention when both parties decide to cooperate in planting an orange tree.