A mushroom is a kind of plant called a fungus. Believe it or not, there is one kind of fungus that loves to hang out on the skin of your feet — especially between the toes. All it needs is a good food supply (like some tasty dead skin cells) and some moisture (sweaty sneakers are great) and this foot fungus can go crazy. Pretty soon you'll have a case of itching, burning, smelly athlete's foot!