Dorodango is a craze sweeping Japan's schoolyards.

Here is the How To Make your own Dorodango:

Step 1 - Pack some mud into your hand, and squeeze out the water while forming a sphere.
Step 2 - Add some dry dirt to the outside and continue to gently shape the mud into a sphere.
Step 3 - When the mass dries, pack it solid with your hands, and rub the surface until a smooth film begins to appear.
Step 4 - Rub your hands against the ground, patting and rubbing the fine, powdery dirt onto the sphere. Continue this for two hours.
Step 5 - Seal the ball in a plastic bag for three or four hours. Upon removing the sphere, repeat step 4, and then once again seal the sphere in a plastic bag.
Step 6 - Remove the ball from the bag, and if it is no longer wet, polish it with a cloth until it shines.

Apparently, kids in Japan love it.

As proof, check out the kids making their dorodangos in this google image search.