Referenced By: The source code for Perl 5 contains several quotes from The Lord of the Rings (and one quote from The Hobbit). Most users of Perl 5 never look at the source code and never see these quotes. The file mathoms.c contains artefacts kept only for compatibility. It quotes the Prologue of The Lord of the Rings, about how the hobbits kept mathoms.
What Could Have Been: Previously unpublished materials have a lot of examples of what could have been.
Aragorn being a ranger hobbit named Trotter was one of them. Later, he was a man whose name kept changing back and forth between "Trotter", "Elfstone" and "Aragorn".
Éowyn being Aragorn's love interest (before Arwen was created)
Éowyn dying on the battlefield defending Théoden and not getting to kill the Witch-King
Anywhere from two to five hobbits setting out on the quest instead of four
The original hobbit names were Bingo (Frodo), Odo (Sam), Marmaduke (Merry), and Frodo/Faramond (Pippin)
A Fellowship that consisted of seven instead of nine members (Legolas and Gimli were later additions, and at one point, another elf was supposed to go as well)
Treebeard and the ents appearing at the last battle in front of the Black Gate (and this is after they act as The Cavalry for Lothlórien)
Boromir arriving at Minas Tirith and completely going over to the dark forces partway through the siege.
Denethor surviving the siege of Minas Tirith (but still suspicious of Aragorn)
Denethor originally being less harsh towards Faramir - in fact, in the first draft, it was Faramir's idea to retake Osgiliath, and Denethor reluctantly agreeing, but Tolkien eventually switched this around to make Faramir more sympathetic.
There was a sequel planned called The New Shadow, set more than 100 years after the events of Lot R, involving an evil cult and boys playing at being orcs. Tolkien got about 13 pages in and decided "screw this."
Academy Award: ROTK is in a three-way tie with Titanic and Ben Hur for the most Oscars won by a single film — eleven. Moreover, the film series The Lord of the Rings won more Oscars than any other film series.
Despite all of the series' wins and nominations, the trilogy's cast was snubbed: the only acting Oscar nomination was Ian McKellen for the first film. Most notably, Andy Serkis was not eligible for being nominated for best supporting actor because his character was CGI.
Granted, it could be less of an Award Snub and more a case of "we can't decide just who to give it to." Every actor spent years working on these films. By Return Of The King, they weren't acting anymore, they had become their characters. You try narrowing it to just one person who deserves an award more than the rest.
Peter Jackson was still putting the finishing touches on the extended cut of Return of the King when it won Best Picture, prompting him to muse in one behind-the-scenes clip (as they were adding the rolling skulls to the army of the dead sequence) about how he could still be working on a film that had already won Best Picture.
DVD Bonus Content: Set the standard for in-depth behind the scenes features, even though most DVD releases still can't compare to the sheer mass of juicy bonus material in the DVD sets, even discounting the extended cuts.
Life Imitates Art: According to behind the scenes material, Viggo Mortensen was a natural leader of the actors and film crew. Sean Astin also ended up more or less taking care of Elijah Wood during filming.
In a scene at the beginning of the first movie, when Gandalf visits Bilbo at Bag End, Ian McKellen inadvertently bumps his head against a wooden beam in the low ceiling. Although unintentional, the actor managed to make the little accident look perfectly natural and very funny, and so it was kept in the final cut.
According the the wiki, the scene where Aragorn deflects Lurtz's thrown knife was an accident. Lurtz was apparently scripted to miss, but the actor accidentally threw the knife right at Viggo’s face, who (fortunately!) managed to deflect it with his sword.
That whole fight scene includes this trope. That headbutt? Completely real. Aragorn getting punched in the ribs? That punch wasn't pulled. Aside from any stab wounds incurred, Lawrence Makaore and Viggo Mortensen were actually beating the crap out of each other. It was mainly because the make-up Makaore was wearing obscured his vision, and the punches that were supposed to be pulled ended up actually connecting. Mortensen just figured that it would be best if he just fought back just as hard rather than yelling cut.
Viggo Mortenson couldn't get the cry of grief and anger right at the scene when the trio think Merry and Pippin were killed. In one take, he kicked a helmet and broke two of his toes. The scream actually fit the mood perfectly, and was used in the final cut.
In Helm's Deep, the army of orcs stomping their feet and weapons before battle was entirely unscripted. It all happened because one of the actors playing the orcs got bored and began stomping his feet and weapons. Then other orc-actors took notice and began to do the same thing. Before long, they all did it, which led to Peter Jackson throwing it in.
When Gandalf, Aragorn, Legolas, and Gimli first arrive at Edoras, there is a shot of a Rohirrim flag fluttering to the ground. The flag had simply slipped loose due to the wind but Peter Jackson threw it in because he liked the symbolism.