You can make HAPPY JOY PLAQUE by combining DOOR and CAVE BACKGROUND. You can find this item in misc blocks category. This thing grows like weed... NOT that weed you silly. HAPPY JOY PLAQUE gives experience points when broken. Hitting it will break it but you need to count the hits yourself. By default you should get at least 1 seed back. Profiting with this might be questionable. Massproducing HAPPY JOY PLAQUE can be tricky. You will find out after you have harvested a few.