1 When they're warm. Cold McDonalds fries are nasssssty. Actually the only fries that aren't nasty when cold are Steak & Shake, and then only with ketchup on them.
2 This is sarabi's theory, which I fully endorse. There must be some sort of highly addictive substance in them. They're greasy, oversalted, cooked under questionable conditions -- don't tell me you worked fast food and never threw pickles in the fry vat -- and just generally disgusting in concept, yet.... we keep going back for more.