So, I don't know about you, but I often don't know what to do with extra cake/muffin batter. Either you wait until your first round of cupcakes/muffins are out of the oven and then clean the tin and fill only a few holes and bake again, or you throw it away. Either option is depressing and annoying.
So, this past winter my mother (hi mom!) gave me individual silicone muffin cups. I admit I had not used them until today, when I had some extra cupcake batter to make exactly two extra cupcakes. I filled the individual silicon cups and put them on a baking sheet along with the rest of the cupcakes. Perfect solution!