An egg with a cute little chick inside. By turning the knob on the side, you can raise and lower the chick, so that it looks like it's breaking out of the shell.
Note that if you push the front panel on very tightly the chick's beak could get caught on the inside. You may need to pull it out a bit to make sure the head can freely move up and down.
I also designed the control knob so that it can be easily removed and replaced with a 1x1 plate, to 'hide' the mechanism. But, depending on the clutch power of your bricks, the 1x1 round bricks might slip. You can just replace the axle with a longer one that extends outside the egg to have a more solid control connection.