Not only are most people surprised to learn that "Die Hard" is based on a book, but the movie also makes some notable digressions from the source material.

Michael Ochs Archives/Getty Frank Sinatra, circa 1960, already 20 years into a phenomenal career that was probably never meant for an action-adventure picture like "Die Hard" ...

And not just any singer - 73-year-old Frank Sinatra. Die Hard, the 1988 action classic that defined a genre, was originally part of a very different cinematic universe.