Thanks Steve, but I am still confused.

Granted if one attached an object to the balloon, it would not expand while the balloon did. But if I understand the metaphor, the surface of the balloon is the two-dimensional substitute for the 3 dimensional world in which we live. We are to suppose that we are two dimensional beings living "in" the surface, not "on" it. There is nothing "outside" or "on" the surface of the balloon, unless it is a 4th or 5th dimensional object.

Sorry if this is taking a metaphor to far, but its always bothered me.