The Otamatone is like no other instrument we've ever seen - and I don't think seeing an instrument in action for the first time has ever made me smile so much. Seriously, take a look at these videos. As you can see in the video you play the notes with one hand on the stem and then squeeze the head to make the mouth sing them. Amazing.
The Otamatone comes in a number of colors and a standard and deluxe version (bigger, louder, and has an audio out).