As you explore area dungeons, temples, and fields, you will encounter little creatures called Chim Chims that you have to kick to collect Chim Spheres to activate obstacles like steam doors, warp points, and steam switches. Chim Chims can be found riding little mine carts in the walls of cave dungeons, in trees, in mushrooms, and large pots. This achievement only requires that you kick 30 of them, but you'll need to kick or ram many more than this in order to complete the Chim Chim campaign.