A calorie is the unit of energy it takes to raise the temperature of 1 gram of water, one degree Celcuis. The calories we see on food labels are actually kilocalories (1000 calories=1 kilocalorie). So a 200 calorie slice of cheesecake (if you can actually find one) is actually 200,000 calories.
But calories don’t just plague our food, they can apply to anything containing energy. In fact, for the health conscious automobile, a gallon (4 litre) of gasoline contains about 31,000,000 calories (actual calories, not kilocalories).
Additionally, if you’re a nail-chewer, know that each nail has about 500 calories. Also, ½ cup of willow tree contains 420 000 calories.