The engineer & the frog

An engineer was taking a walk when a frog spoke to him and said, "If you kiss me, I'll turn into a beautiful princess." 
He picked up the frog and put it in his pocket. 
The frog spoke again and said, "If you kiss me and turn me back into a beautiful princess, I'll become your girlfriend." 
The engineer took the frog out of his pocket, smiled at it and put it back into his pocket. 
The frog spoke again and said, "If you kiss me and turn me back into a princess, I'll become your wife." 
The engineer took the frog out of his pocket again, smiled at it and put it back into his pocket. 
Finally, the frog said, "What is the matter? I'm a beautiful princess. Why won`t you kiss me?" 
The engineer said, "Look, I'm a busy engineer. I don`t have time for a girlfriend or a wife, but a talking frog, now that's cool."