A joker is a little fool who is different from everyone else. He's not a club, diamond, heart, or spade. He's not an eight or a nine, a king or a jack. He is an outsider. He is placed in the same pack as the other cards, but he doesn't belong there. Therefore, he can be removed without anybody missing him.
Jostein Gaarder, The Solitaire Mystery
difference, joker, loneliness, stranger