The Crying Game

A scorpion wants to cross a river, but he can’t swim. He asks a frog, who can, if he can hitch a ride on the frog’s back. "You’ll sting me," says the frog. "It would not be in my interest to sting you," says the scorpion, "because then I would drown."

The frog thinks about the scorpion’s logic, finds it impeccable, agrees to take the scorpion on his back, and then braves the waters. Halfway across the river, the frog reels a burning spear in his side; the scorpion has stung him after all. As they sink beneath the waves, the frog cries out, "Why did you sting me Mr Scorpion, for now we both will die?" "I can’t help it," replies the scorpion, it’s in my nature."
 (From the movie "The Crying Game" 1992)