One day, a wife goes up to her husband and asks for twenty dollars to buy meat.
"Are you crazy?" says the husband, who pulls her over to a mirror. "Let me show you something? This twenty-dollar bill is mine. The one in the mirror is yours. Get it?" The wife nods. The next day, the husband returns home to find a freezer full of meat. Angry, he asks his wife about it. She pulls him over to the mirror and lifts up her skirt.
"See the one in the mirror? That's yours. This one is the butcher's."