Note: A related anecdote appears in Carpenter's "That Not-So-Silent Sea" - an appendix to Donald F. Theall's "The Virtual Marshall McLuhan" (2001)...

"One day [Marshall and I] were swapping "Greatest Invention" jokes ... I told him of an elderly farm woman who quietly proposed "Screens, to keep out the flies." To which Marshall replied, with equal gravity, "the electric shaver": for ten years he'd avoided looking in a mirror." (pages 249-250)