An economics graduate student was crossing a road one day when a frog called out to him and said, “If you kiss me, I’ll turn into a beautiful princess.” He bent over, picked up the frog and put it in his pocket.
The frog spoke up again and said, “If you kiss me and turn me back into a beautiful princess, I will stay with you for one week.” The graduate student took the frog out of his pocket, smiled at it, and returned it to his pocket.
Desperate, the frog then cried out, “If you kiss me and turn me back into a princess, I’ll stay with you and do anything you want.” Again the grad student took the frog out, smiled at it and put it back into his pocket.
Finally, the frog asked, “What is the matter? I’ve told you I’m a beautiful princess, that I’ll be your girlfriend and do anything you want. Why won’t you kiss me?” The grad student said, “Look, I’m an economist. I have no idea what it would even be like to have a girlfriend. But a talking frog has got to be worth a fortune.”