When I was in high school there was a guy in the class below us that ate a slice of pizza every day for lunch and every day brushed the box onto the ground in the outdoor seating area and walked away. We started collecting them and when we had a few dozen we filled his locker with them with a note not to be such an inconsiderate asshole. Enough people saw them come tumbling out of his locker that shaming him for littering became a popular meme for a while and he was really self conscious about it after that. It felt soooooo good.