Trivia: The puppet used for physical shots of Treebeard was 14 feet tall.
Trivia: Edoras' filming location was a national park. They could only film there under the condition it was left exactly as they found it. As such a lot of the natural vegetation had to be carefully removed and stored for the 16 months of filming, then replaced.
Trivia: The raw fish Gollum eats was in reality a fish shaped lollipop.
Trivia: To make the inside of the Orcs' mouths black, the actors playing them used a liquorice mouthwash just before filming.
Trivia: When Elrond gives Arwen his hard-father talk before sending her away, he asks, "Do I not also have your love?" and she replies, according to the subtitle, "You have my love, father." Actually she said, "Gerich veleth nín, Ada." Adar = "father", but Ada = "papa". One of many nuances lost in translation in the films' subtitles. (01:26:00)
Trivia: You may notice that in every shot of the Hobbits, they are always walking or riding from the left side of the shot to the right. This was done deliberately to give the impression that they are journeying towards Mount Doom at all times.
Trivia: During the filming, Viggo Mortensen (Aragorn) and Orlando Bloom (Legolas) would rib each other quite a lot. Mortensen would tell Bloom to go brush his long, blond hair and get another manicure, because the Elves are so prissy. Bloom would call Mortensen a dirty human (which is entirely true as he rarely bathed during filming) and say that at least the Elves live forever (which is entirely false and is based on a popular misconception of how long they live).
Trivia: The rain during the battle of Helms Deep is mostly real rain (as opposed to the product of a rain machine, as is normally the case).
Trivia: When an elf soldier falls off the battlements during the Helm's Deep Battle, he yells a Wilhelm scream.