Walking into Rosa's Fresh Pizza in Philadelphia is a little bit like walking into your most prankable coworker's cubicle while they're on vacation -- it's covered in Post-it notes. But the reasoning behind the ones at Rosa's is a whole lot nobler. The owner, Mason Wartman, instituted a pay-it-forward slice policy wherein customers can pay an extra $1 to buy a slice in advance for the homeless. And each Post-it is a unit of currency.
If someone wants a free slice, they can simply take a Post-it from the wall and exchange it at the register; in the nine months that the policy has been in place, over 8,400 slices of pizza have been paid for in advance by charitable customers. That's so many that the Post-it note system eventually had to be scrapped in favor of a more organized method (Wartman keeps track at the register), but now, each paper affixed to the wall is adorned with sentiments of gratitude for the free food.