When I was growing up, my Grandmother had one of these plants in her front garden.  We used to pull off a leaf, press it with our fingers until the “skin” separated from the fleshly center, tear the stem end off the leaf, and gently blow into it.  It was fun to watch the leaf puff up like a “frog belly”.  This was a simple way to entertain yourself on a hot summer afternoon.  🙂