The Little Girl Who Cries Wolf

Yep, she sure does.  Whether it is pretending to have to go to the bathroom or pretending to be hurt, she likes to cry "wolf."  Under a great amount of frustration I told a quick version of why we do not, under any circumstance, pretend to be hurt when we are not.  It has not stuck.  It continues...and with it grows my frustration.  Any suggestions as to how to curb this new form of entertainment?  I think tomorrow we will be taking a trip to the library where I will pick up a book (or twelve!) about this topic.  Let me know what all you Mommy blog-buddies have to say about this.  Thanks.