Here's the effect I'm trying to produce:
a) A square-shaped object is on top with a circular-shaped object underneath, then clicking on the square will cause the square to vanish revealing the circle and causing other objects on screen to appear as well. Then, c) Clicking again on the circle will then reveal the square overtop and vanish the other objects on screen.

In order to create this effect I somehow need to create an object that sits on top of another one, that allows clicks to pass through it. Can anyone tell me how to achieve this effect? I thought I read somewhere it was possible, but that was a long time ago. the resulting object set will be something quite a few people will be happy with.