Author Existence Failure: Frank Herbert died in 1985, leaving the Dune series on an apparent massive cliffhanger. His son and Kevin J. Anderson continued the series to mixed critical and reader response.
Beam Me Up, Scotty!: Several quotes from the original film are widely assumed to be from the novel:
It is by will alone I set my mind in motion. It is by the juice of sapho that thoughts acquire speed, the lips acquire stains, the stains become a warning. It is by will alone I set my mind in motion.
Sting and Kyle MacLachlan, both in their mid-late 20s, played the 15 year olds Paul Atreides and Feyd Rautha in the '84 film.
The miniseries also did this, and in Children of Dune the nine-years-old Leto II and Ghanima were played by mid-twenties actors, and the miniseries twins' ages were upgraded to nearly 18 for this very reason.
Deleted Scene: Several scenes were cut from the theatrical release of the 1984 film and later restored to the extended versions, which is part of why they're so much longer. Of these, one of the most significant is the death of Thufir Hawat, a powerful scene in which Paul separates Thufir from the captured Harkonnen and offers him his life, only for Thufir to commit suicide rather than kill Paul. This omission creates something of a What Happened to the Mouse? moment in the original cut, as Thufir—one of the film's more important characters—can clearly be seen standing among the prisoners (between the Emperor and Gaius Mohiam) in one shot, and simply vanishes in the next; his disappearance is never explained.
Doing It for the Art: Dune contains a sprawling universe adorned with myriad details and complicated histories, economics, and ecology. Frank Herbert loved to show his work, as detailed below. It began as work for a newspaper article ("They Stopped the Moving Sands"), but he became so enthralled that it became a passionate epic. He never even got around to finishing that article.
Executive Meddling/Screwed by the Network: Dino De Laurentiis pared the film down by hours and the result was a confusing mess to many people who didn't read the book. It was such a negative experience for Lynch that he actually turned down the chance to do a director's cut years later and had his name taken off the extended version that was made without him, so while the extended version does expand on and explain the overall universe and setting better it's still mostly guess work.
Frank Herbert and Willis E. McNellynote Author of the Dune Encyclopedia began collaborating on a prequel novel focusing on the Butlerian Jihad. It also was abandoned due to Herbert's death.
Ridley Scott was at one point slated to direct a film adaptation of Dune. Peter Berg had been the front-runner to direct a new remake in the early '10s, before the project fell into Development Hell.
Val Kilmer was reportedly almost cast as Paul in the 1984 film version.
The late Christopher Reeve of Superman fame was reportedly considered for the role at Paul in one of the earlier pre-Lynch periods - which makes the casting of Kyle Mac Lachlan even funnier as he would later voice Superman in the animated feature Justice League: The New Frontier.
Jack Nicholson was reportedly considered for the role of Gurney Halleck at one point.
The Alejandro Jodorowsky version would've cast Salvador Dali as the Emperor, Orson Welles as Baron Harkonen, and Mick Jagger as Feyd. Jodorowsky had cast his son as Paul Atreides, who spent several months training in martial arts and other various fighting styles before the project was shelved.
Also, Jodorowsky had intended to have the ending of his film be vastly different from the book, having Feyd killing Paul during hand-to-hand combat in front of the Emperor. But as he dies, Paul's consciousness then infuses into the planet Arrakis. Paul then mocks the Emperor, by moving about from person to person, including Alia, Stilgar, and Irulan, who when inhabited, all speak in Paul's voice. The non-corporeal Paul, fulfilling the prophecy of the Kwisatz Haderach, then causes Arrakis' terraforming to occur immediately, with the skies turning a brilliant blue. The movie then ends with the planet breaking orbit, to roam throughout space, to re-educate the universe.