Mr. Arkadin (Confidential Report) (Orson Welles, 1955)

And now I'm going to tell you about a scorpion. A scorpion wanted to cross a river, so he asked a frog to carry him.
"No", said the frog. "No, thank you. If I let you on my back you may sting me, and the sting of the scorpion means death.
- Now where
", asked the scorpion, "is the logic of that? No scorpion could be judged illogical. If I sting you, you will die - I will drown."
The frog was convinced and allowed the scorpion on his back, but just in the middle of the river he felt a terrible pain and realized that after all the scorpion had stung him.
"Logic" cried the dying frog, as he started under, bearing the scorpion down with him. "There is no logic in this.
- I know", said the scorpion, "but I can't help it - it's my character."

First published the 21st of February, 2005 on http://achernar.over-blog.com/article-129350.html.