What do you do if your muffins are not fully cooked?

If you are making muffins and you run out of batter before you fill all your muffin cups, add a couple of tablespoons of water to the empty cups. You can warp the muffin tin if you bake it with some of the cups empty. Most recipes make a dozen muffins, but on occasion I too have more muffin cups then I have batter for. By using my method of adding water to the empty cups, I have never warped a pan.