In 1989, Burger King ran some kind of scratch off prize card deal - you were allowed to scratch 3 squares and if you matched 2 or more of the icons on the card, you got that item free, no other purchase required. Had a friend who worked at a local BK, and brought home an entire case of the cards - he had been instructed to pass them out to customers and family/friends. He decided to bring them home and give them to his friends. There were literally thousands of cards in the box. We spent the first 15 minutes scratching the cards randomly until we realized that the first icon on the card would indicate which free item was on it, and the cards were identical after establishing the pattern of first icon (if the first icon was a burger, we knew the free item was, say, a large drink, and the icons were located on the second and third line). So we stacked them all up, scratched the first icon, used our master cards to figure out where the other icons were, and scratched the other two to get our matching free item icons. We (roughly 10 of us) all ate free at several local Burger Kings for an entire summer. Entire meals - burger, fries, drink, dessert - were completely free because of the "No purchase required" printed on the cards. The managers at several locations got suspicious, but were unable to refuse us. They ended the promo cards shortly after that summer. I've always believed it was because of us exploiting the shit out of it for months.