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.
The Solitaire Mystery (ed. Hachette UK, 2010) - ISBN: 9780297864066