Black Cats and Luck
Depending on one's area of the world (and the century one lived in), black cats portend either good or bad luck. Here are some examples, a couple of them quite involved, with some tongue-in-cheek asides. In Asia and the U.K., a black cat is considered lucky.
In Yorkshire, England, it may be lucky to own a black cat, but it is unlucky have one cross your path. To dream of a black cat is lucky.