The Scorpion and the fox

Once upon a time, there was a fox who was about to cross a river, when suddenly he saw a scorpion. The scorpion needed to travel upstream, but he could not swim. So he went to the fox and explained his problem. "Let me ride on your back while you swim in the river." But the wily fox would have none of it. "You are poison. You will sting and kill me, and we will both drown." But the scorpion gave him his solemn oath not to sting. "I would be crazy to do that, my friend. We can both arrive safely at our distination."

So the fox took the scorpion on his back. "Hold on tight," he said. "Have no fear," the scorpion said. They had gone some distance in the water and were in the deepest part when the fox felt the sting of the scorpion upon his neck, then the pain, and he was beginning to thrash and sink. He moaned, "But you promised..." The scorpion, with his last breath, shrugged it all off: "Stinging is my nature; I can't help it."