Not from Lord of the Flies.
From the website of Jason Shelowitz, which features his Subway Etiquette signs. For contemplation while living through this, New York City's historic pocket of no-subway time:
Don't be a piggy.
Discovered while passing through the site of Jeremiah, possibly still hunkered down in the East Village (as opposed to another location).
Better than "Don't Be a Litterer."