Strangely enough, my father explained it to me.
9. THE INFAMOUS INNUENDO AT THE END WAS ALL HITCHCOCK.
One of the things North by Northwest is famous for is its concluding shot of a train entering a tunnel, which serves as a visual pun for the main characters’ planned night of romance. Hitchcock considered it one of his finest, naughtiest achievements. And he gets all the credit, too: Lehman’s screenplay just ended with “the train heads off into the distance,” or words to that effect. “There’s no way I can take credit for [the tunnel],” Lehman said, adding: “Dammit.”
Your old man was like, “If I don’t explain a few things to this kid, I’ll never have any grandchildren!”