The studio deemed [the original] ending too frightening, and it insisted that director Don Siegel add a prologue and epilogue implying that the invasion would be defeated. Siegel reluctantly agreed, grumbling that pod people had taken over the film industry. The change blunts the picture's paranoid vision: Though the director's cut shows us a world where the agents of psychiatry and law enforcement are completely malevolent and untrustworthy, the studio version ends with Miles breathing a sigh of relief as a psychiatrist alerts the FBI to the invasion.
But in either incarnation, it is a harrowing and disturbing film. The story may be science fiction, but it's rooted in a familiar experience. "I've seen how people have allowed their humanity to drain away," Miles mulls to Becky in one scene. "Only it happens slowly instead of all at once." The film's star, Kevin McCarthy, proposed an alternative title for the film, which Siegel liked but the studio rejected: "Sleep No More."
I don't mention this in the book, but my favorite story that plays with the body-snatcher idea is Daniel Pinkwater's 1976 novel Lizard Music, a tale in which the pod people, like the conformity they represent, are not an abrupt invasion but a background fact of life. "Don't the pod people worry you?" one character asks another. "Worrying about them is a good way to become one," comes the reply.