An Engineer Joke

An engineer 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 forever."
The man took the frog out of his pocket, smiled at it and returned it to the pocket. 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 man 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 stay with you forever and do anything you want. Why won't you kiss me ?"
The man said, "Look I'm an engineer. I don't have time for a girlfriend, but a talking frog is cool."