When you get a solid fart brewed up, fart into your cupped hand and throw it into your friend's face.

While performing said action, exclaim "Ninja, vanish!!!" in a loud, possibly Asian accented voice. While your victim is blinded by your noxious gift to the face, get the hell out of there like a ninja.

When a girl is about to cum pulling out and throwing sand in her pussy and screaming "Ninja Vanish." Then running out of the room.

When an individual flatulates in public and promptly flees the area prior to acknologement of the foul odor.