Apologies for the double-post.
In a Hall of Mirrors, there is a mirror in the backroom that, if someone is wrong, they are vanished into thin air. An ugly lady walks up to the mirror and says, "I think I am the most beautiful woman in the world." She vanishes. A fat lady walks up to the mirror and says, "I believe I am the thinnest woman in the world." She vanishes. A blonde walks up to the mirror and says, "I think-" She vanishes.