Does addChild work with masks?

Perhaps I’m missing something about masking or the display list, but here’s my problem:

I have a clip with an animation, a mask and a static image I load under the mask. If I place the image there myself, everything looks fine. I am trying to use add/remove child to dynamically change which image is displayed under the mask.

So in the layered that is masked, I have a blank MC named “container”, into which I am trying to load an image. Just using one for test purposes like so:

bulb.container.addChild(new iconShot());

If I make the mask layer invisible, then everything shows up. If I use the mask layer, then the clip underneath it never shows up. Any ideas why?

Just found out that if you must mask the main movieClip/Sprite plus its children, it you want the contents to show up.