A scorpion approached a frog on the side of a river. Listen Frog, I was wondering if you could carry me across the river, I need to get to the other side". The frog replies, "Why would I do that, you're a scorpion, you'll sting me".
The scorpion say, "No I won't, because if I sting you, you'll die, and I'll drown". The frog thinks for a moment and says "good point".
Half way across the river the scorpion stings the frog. The frog is dying from the poison and the scorpion is drowning. The frog says "Why'd you do that? Now we are both going to die."
"Because I'm a scorpion", it replied.