When you're having sex doggy style, light up a cigarette and stick the butt end of your partners asshole so it protrudes out like a candle in a birthday cake. When you climax, aim your load at the cherry of the cigarette to extinguish it before the ember burns all the way down to your partner's asshole.
A rumor that gets spread so fast that everyone knows it in at least 30 seconds.
Lets say that you never got a girlfriendin your life and you tell your friends at school at work. Since you told them its your first girlfriend they start to spread it and becomes a uncontrollable wildfire.