When the wrong number turns into something right... :

1955 – An ad by a Colorado Springs-based Sears store in the Colorado Springs Gazette-Telegraph appeared with a telephone number encouraging children to call Santa Claus.  Unfortunately, the phone number given was a misprint and was actual the number for the Continental Air Defense Command (CONAD) Operations Center in Colorado Springs.  On the upside, this simple error led to the current NORAD Tracks Santa program.