This song was Inspired by an actual event as described in The Flying Saucer Reader
by Jay David (1967). It seems that a group known as the "International Flying Saucer Bureau" sent a communiqué to all its members asking them to participate in an experiment termed "World Contact Day." Basically, they said that at a predetermined date and time, all the members should try to simultaneously send a telepathic message into outer space, in hopes of contacting Extra Terrestrials. The actual message they 'sent' started with the words "Calling occupants of interplanetary craft!"
Terry - St. Johns, Canada