* AllStarCast: If you were an A-List male actor in Hollywood in 1962, you have at least a bit part in this film. Plus a couple well-known British, French and German actors.
* ArtisticLicenseHistory: Engineers are seen removing explosives from the Orne Bridge. In reality they hadn't been placed in their slots when the gliders landed. Zanuck chose to ignore Howard's telling him this for the sake of drama.
** Averted when a scene where German soldiers are seen running out of the café near that bridge wasn't shot, as one of the owners insisted vehemently she had never allowed Germans to sleep there.
* AsHimself:
** Almost. Actor Richard Todd plays John Howard, the Major whose unit secures Pegasus Bridge. One of the relief units coming to their aid was led by Captain Richard Todd, played by another actor in the movie! There is a picture of Richard Todd, as John Howard, posing next to the other actor, as Richard Todd.
** Another almost with former President UsefulNotes/DwightDEisenhower. Eisenhower actually would have played himself except he looked too old for his younger self from two decades before so the idea was scrapped.
** Played straight with Joseph Lowe, one of the cliff climbers at Utah Beach who reprised his efforts for the movie.
** Also played straight by Bill Millin, the bagpiper with Lord Lovat's commandos.
* BackedByThePentagon: About 23.000(!) real US, British and French soldiers were used as extras in the movie. They also rented two Messerschmitts from the Spanish air force and four Spitfires from the Belgian air force.
* CastTheExpert:
** Richard Todd, who plays Major Howard of the British Airborne, was a British paratrooper during the war and actually took part in the D-Day landings -- in fact, he was initially approached to play ''himself'' in the film.
** As a 22-year-old private, Joseph Lowe landed on Omaha Beach on D-Day with the Second Ranger Battalion and scaled the cliffs at Point-Du-Hoc. He scaled those 100-foot cliffs all over again, for the cameras, some 17 years later.
* TheDanza:
** Sort of. Gen. James Gavin, played by Robert Ryan, was actually born James Ryan, but put up for adoption at age two, and adopted by Martin and Mary Gavin at age seven.
** Creator/RichardBurton plays Richard Campbell.
* DawsonCasting Creator/JohnWayne as Lieutenant Colonel Benjamin Vandervoort. The real Benjamin Vandervoort was 12 years younger than Wayne, and on D-Day he had been just 27, while Wayne was '''54''' when the movie was filmed.
* DeletedRole: Dewey Martin, whose character was named Lt. Wilder, was deleted from the final cut.
* DirectorDisplacement: Given ''five'' people did the thing simultaneously, doesn't surprise producer Darryl F. Zanuck gets more focus than all of them.
* MoneyDearBoy: This was one of several high-profile projects which Creator/JohnWayne took in the wake of the extremely expensive ''Film/TheAlamo''. He had used his own funds to help finance the project, and he was in desperate need of a quick payday.
* PlayingAgainstType: Red Buttons usually played goofy comic-relief or funny hero types. Here, while there's some humor with him, his main scene is one of the film's most horrific parts.
* RealLifeWritesThePlot:
** Creator/RichardBurton and Roddy [=McDowall=] asked for small roles to spare the boredom after ''Film/{{Cleopatra}}'' was delayed... AGAIN.
** Creator/SeanConnery, on the other hand, also has a small role because he was eager to get off to Jamaica and begin filming ''Film/DrNo''.
* RetroactiveRecognition: Before he became famous, Creator/{{Loriot}} got cast by Bernhard Wicki in an uncredited bit-part as a junior Wehrmacht staff officer.
* ScrewedByTheNetwork: Averted - Fox was planning on just doing a quick wide release to earn some cash they needed to offset their losses from ''Film/{{Cleopatra}}''. Darryl Zanuck threatened to bring''The Longest Day'' to Warner Bros. if they didn't do a proper roadshow release, and Fox had to comply. (it still was the box office hit the studio needed)
* ThrowItIn: While clearing a section of the Normandy beach near Pointe du Hoc, the film crew found a tank used in the invasion. They cleaned it up and used it for the British Invasion scenes.
* WhatCouldHaveBeen:
** Creator/ChristopherLee, who fought in the War as an intelligence officer with the RAF, auditioned for any role he could get. He was turned down because the producers felt [[{{Irony}} he didn't look like a military officer]].
** This was made just after UsefulNotes/DwightDEisenhower's presidency and the producers very nearly '''cast Eisenhower to play himself'''. They abandoned the idea because he was too old, though.
** Creator/JohnWayne's role was originally offered to Creator/CharltonHeston.
** Creator/AlecGuinness was sought for a cameo.
** The part of the British padre was first offered to Creator/DirkBogarde, who turned it down.
** Creator/BrigitteBardot and Marina Vlady turned down the role of Janine Boitard.
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