Polymorphism shouldn't be a new concept to anybody. You deal with it every day in the real world....Let's say for example you want to fuck a hole. You fuck all holes the same. You don't care if that hole happens to be a mouth, an ass, or a pussy, you're gonna fuck it the same way regardless. However, the mouth, pussy, or ass may respond differently to the fucking...
Finally somebody gets away from shape, animal, and device driver examples! Further, it is proof that OO is fscked :-)