For urban dwellers, dollar slice pizzerias are the comfort food constant to city life: everyone has their favorite, but they aren’t going to make or break your culinary experience. But at Rosa’s Pizzeria, a dollar slice joint in Center City, Philadelphia, business is about much more than churning out greasy paper plates. At Rosa’s, each slice costs a dollar, but for one or two more dollars, you can buy extra pizza to help feed the homeless of the neighborhood. Rose’s has become known in the area as the “pay it forward” pizzeria.

It all started, owner Mason Wartman told the local ABC affiliate, soon after he opened his pizzeria last year. One day, a customer came in and asked if he could buy an extra slice for someone in need. Right away, Wartman stuck a Post-it note to the wall with a simple smiley face on it. Nine months later, that customer has started a chain of kindness, and the wall is littered with thousands of Post-it notes, representing the good deeds that pizza fans have done for those in need. Some recipients sign the colorful slips of paper writing encouraging notes like, “You are beautiful,” and “You can do it!”

"This guy wrote on a paper plate "God bless you. Because of you I ate off this plate, the only thing I ate all day," Wartman told ABC.

Wartman also sells t-shirts and sweatshirts, the proceeds of which go toward buying more pizza for the local homeless. He has sewn resources for the homeless inside each article of clothing.