It's basically one of those small plastic measuring tapes that you pull out and press a button to make the tape shoot back in. You pull the leaf and PRESTO! Then just squeeze the apple and it's back to normal.
This little thing was just so fun to make. I got the idea from some swap items I received made by other people. I have a Mary Poppins hat where you pull the flower out for the tape, and a cupcake one where you pull out the cherry on top. Super fun, cute, and USEFUL!