How do you get fire in Super Mario Brothers ds?

Answer 1

Certain item boxes (the yellow blocks with the ? on it) have power ups inside. When you hit one, a red mushroom will probably pop out of it. If you run over the item, Mario will grow to twice his normal size. If you hit another item box while at this size, a flower will sprout out the top of it. Step on the flower and Mario will have fire powers.