In Brazil, "catadores" collect junk and recyclables. But while they provide a vital service that benefits all, they are nearly invisible as they roam the streets. Enter graffiti artist Mundano, a TED Fellow. In a spirited talk, he describes his project "Pimp My Carroça," which has transformed these heroic workers' carts into things of beauty and infused them with a sense of humor. It's a movement that is going global.