Director Ralph Bakshi had originally planned to use music by Led Zeppelin in the film, but was unable to get the rights. Led Zeppelin were known as being fans of the books, with several of their songs, "Misty Mountain Hop", "Over the Hills and Far Away", "The Battle Of Evermore", "Ramble On", referencing imagery and characters from Tolkien's books.
Peter Jackson first encountered The Lord of the Rings via Bakshi's film, and some shots in his live-action trilogy appear to have been influenced by it. One such shot features Frodo and the other hobbits hiding from a Black Rider under a big tree root, while the Black Rider stalks above them. In his version of the sequence, Jackson uses a similar shot, although he films it from a different angle (in the book, Frodo hid separately from the other hobbits). A second sequence features the camera slowly revolving around Strider and the hobbits, who stand in a circle as the Black Riders approach them on Weathertop. In his staging, Jackson also uses a similar shot, although his camera is much faster, and Strider is not amongst the hobbits. A third similarity is the depiction of Gollum losing the ring in the prologue: both films show very similar events, but the book had no such prologue, and indeed it runs directly counter to Tolkien's scheme for the storyline. Another similarly staged scene is Legolas, Gimli, and Aragorn's discovery of Gandalf the White.
Director John Boorman originally envisioned making the entire trilogy as a single one hour and forty minute film. Ralph Bakshi heard that he was going to do this, and, as a fan of "The Lord of the Rings" trilogy, and J.R.R. Tolkien, was horrified. When Boorman's plans to bring Tolkien's novels to the screen fell apart, Bakshi approached J.R.R. Tolkien's daughter to do the novels as a trilogy of animated films. Tolkien's daughter loved Bakshi's fantasy Wizards (1977), so she gave him the rights to The Lord of the Rings. Bakshi filmed "The Fellowship of the Rings" and "The Two Towers" (which were collapsed into a single two-and-a-half hour film), and had planned to film "The Return of the King", but the trilogy was never completed.
At one point in the film's development, studio executives thought that the names "Saruman" and "Sauron" were too similar, and would confuse the audience, and decided that Saruman should be renamed "Aruman". This decision was eventually reversed, but some references to "Aruman" remain in the finished film.
On the DVD commentary of "The Lord of the Rings: The Fellowship of the Ring," Peter Jackson acknowledges one shot, a low angle of a hobbit at Bilbo's birthday party shouting "Proudfeet!", as an intentional homage to Bakshi's film. By far the biggest "lift" however is the scene of the Nazgûl appearing in the room at Bree and slashing the beds to ribbons thinking the shapes under the sheets to be the hobbits. This is almost identical to Bakshi's version which is significant as the scene is not depicted as described in the book: in the book, the attack is carried out by the Nazgûl. Some of Sam's interjections are also sourced from Bakshi rather than Tolkien.
Many Tolkien fans were disappointed that this film only covered the first two books, and by how some major characters and events were cut from the film. When Saul Zaentz told Ralph Bakshi that he will not allow the film to have a sequel, Rankin and Bass made an animated adaptation of The Return of the King. After that was released, many of those disappointed fans changed their minds, stating that Bakshi's film was a more mature and detailed adaptation of Tolkien's stories.
During the battle of Helm's Deep, a song with non-English lyrics is heard on the soundtrack. The words Isengard, Mordor, and Sauron can be clearly discerned. The song is not in any of Tolkien's invented languages, instead Composer Leonard Rosenman had his choir sing nonsense lyrics to get the desired effect. According to the liner notes of the CD soundtrack, part of the lyrics also include the composer's name backwards.
Many of the actors portraying the physical parts of the characters in this movie provided the voices. Other characters, such as the Hobbits, were portrayed by animators and by Billy Barty in the live-action footage, and then voiced by other actors. The actors who play physical parts but not voices are credited as "Character Actors".
Author J.R.R. Tolkien was friends with author C.S. Forester, and two of the Hobbit families in the Shire mentioned by Bilbo, the Bracegirdles and the Hornblowers, are a tribute to Forester's Horatio Hornblower novels.
Trey Wilson, who played Nathan Arizona in Raising Arizona (1987), did the live-action stand-ins for Aragorn whenever they would blend in the animation scenes with live-action sequences through out the movie.
Cel animation was produced and shot for this film, but was cut out at the last minute. Only a few brief segments of the film were drawn from scratch, with much of the film rotoscoped, and some sequences combining non-rotoscoped live-action footage with animation.
Sharon Baird did the live-action stand-ins for our hero, Frodo Baggins, whenever they would blend in the animation scenes with live-action sequences throughout the movie. While the late John A. Neris stood in for Gandalf, The Wizard, the late Billy Barty stood in for Bilbo Baggins and Samwise Gamgee, young Dennis Madalone played Prince Isildur, and Mic Rodgers played Marshal Eomer, Theoden's nephew.
The late William Squire also played the voice of the Narrator and Dwimmerlaik, The Witch-King of Angmar (The Lord of The Nazgul). But they cannot be seen on his list of characters he played on the credits.
Rumors say that Anthony Daniels also played the voice of Deagol, Smeagol's cousin. While rumors say that the late John Westbrook also played the voice of Lord Celeborn, the late Alan Tilvern also played the voice of Odo Proudfoot, and the late Michael Deacon also played the voice of Grishnakh, The Mordor Orc Captain who tried to steal Merry and Pippin away from Ugluk and his Uruk-Hai squad.
Terry Leonard (who played Hawk, Remy's gang member in Barquero (1970), and the Nazi van driver in Raiders of the Lost Ark (1981)) appeared as a bald customer wearing earrings at The Prancing Pony, while Hank Calia appeared as a mustachioed customer wearing a red hooded cloak, and the late British comedian Mel Smith (who played The Albino in The Princess Bride (1987)), as a red-hooded customer taking a big gulp of his drink.
Anthony Daniels (Legolas) is best known for playing C-3PO in the Star Wars saga. In that role, he worked opposite actors from several other Tolkien adaptations. The Rancor's keeper in Star Wars: Episode VI - Return of the Jedi (1983), was played by Paul Brooke, who also played Grima in the BBC Radio drama. Count Dooku was played by Sir Christopher Lee, who also played Saruman. Poggle the Lesser was originally voiced by Marton Csokas, who also played Celeborn. A Naboo guard was played by Richard Armitage, who played Thorin Oakenshield. Bruce Spence (Tion Meddon) was also the Voice of Sauron. Lastly, Supreme Leader Snoke was played by Andy Serkis, who also played Gollum.