Grasp the bottom right-hand leaves with your right hand. With your left hand you pull down on the top leaves, in a counter-clockwise direction. The picture morphs!
Start position: sleeping pumpkin.
End position: awake pumpkin.
I was looking through one of my old favorite books,
and thought I would try a Changing Picture, also known as a Magic Circle.
I decided to do a sleeping pumpkin/awake pumpkin.
Here's a video (not mine) showing the mechanism in action.
After it's put together it can be glued to a card without impeding the sliding motion. Unfortunately, if you turn the top tab clockwise (the "wrong" direction) the circles come apart! I have to think about it a little more and figure out where to put a "stopper" to keep that from happening.
Here's the change sequence.
If you're looking for a rectangular changing picture card (also called a cross fade card), there are instructions and templates in this books.
It's on page 117 of Rob Ives' book, which you can preview on Google books.