I have in my head a sort of pop up card, but it doesn't pop up - you pull a tab and it changes from one image to another. So I think there's slits in the first image, which when the tab is pulled, fragments of the second image slide through the slits and form a complete image, concealing the original image...?? Or if the second image is in one piece that would be even better.
I'm sure I've seen these before, probably back in my childhood through the dark depths of time. But WHAT are they called?? I have googled and googled and cannot find what I'm looking for. My small brain can't work out how I would make such a thing on its own.
Many TIA!