When I was about 5 or 6 years old, McDonald's ran a seat belt campaign, where you'd get to check off a box on a card for every time you put on your seat belt, and when the card was full (about 25 boxes) you could turn in the card for an ice cream cone or a box of cookies. I remember it was such a special day when mom would buy me a box of those Ronald McDonald and Friend's shaped cookies or a soft serve cone. I think secretly she liked to get me the cookies because she could snag a few, but the cone was ALL MINE. So being the kid who would do anything for a sweet, I was VERY excited about this little card mom showed me.
When I was little we never wore seat belts in the car. In fact, the seat belts for the back seat were under the seat, and once this card of boxes came into my life, I insisted they be pulled out. With the power of this card, I became a tyrant to the seat belt rule in the car. Every time we were in the car I'd make sure everyone had on their seat belt.
After about ohh... 5 days, I had filled up that card. Mom took me on many errands so I had many opportunities to make a habit of this new rule. And still to this day, the car does not leave PARK until everyone in the car has a seat belt on. So even though I've had many a cheeseburger, chicken nuggets, french fries and ice cream sundaes since then, I still remember that day I walked up to the counter with my full card in hand to get my ice cream. I guess McDonald's had some good effect on me as a kid.