(Guilty! I don't go for the Lucky Charms but a bowl of rice cereal with a bit of sugar always made a good snack for me. And yes I did usually wake up hungry. Just didn't know why)
Lucky Charms can be a great snack during the day. While it isn't very healthy, if you are active through your day, you should be fine. However, when you eat sugary cereals late at night, you are asking for trouble. Foods high in sugar will mess up your blood sugar levels and most likely make it hard for you to sleep throughout the night. You will wake up a few hours later feeling hungry and possibly even with a headache. Instead of having a bowl of sugary cereal, try having some oatmeal or other hot cereal that is low in sugar.