Rescuing the Princess
A long long time ago Hostess chips (was the major brand in Canada at the time) had a Mario Bros promo. You got a “bingo” card in each bag of chips and every card was a winner. You had to scratch 3 of 9 areas and if you matched the icons you won.
One of my friends figured out that using a tin can with a tiny hole punched in the bottom and then dropped down unto a 100W lightbulb, you could see through the card and find the winning spots to scratch.
This spread around town and a week later there wasn’t a single bag of chips to be found anywhere. Sold out all over town. We all had garbage bags of open chips around. I won 1 grand prize which was a Super Mario Bros game.
Story credit: Reddit / Frozen-assets