When an imposter is spotted because the person he's impersonating is in the group/room with, or is himself, the person they're trying to deceive. In its basic form, the conversation will go like this: "Jonesy" comes from this page (and the one before it) of The Adventures of Dr. McNinja #1. If you have a good enough disguise, you might still be able to get away with bumping into the person you're impersonating if you convince them that you are actually their reflection in a mirror. Those liable to Poser Hating are also generally vulnerable to this. Compare I Am One of Those, Too, I Am Spartacus.