Nicolas Cage has said that during the filming of this movie, he ignored all of his acting instincts and played the part of Charlie Kaufman exactly as director Spike Jonze asked him to. He then received an Academy Award nomination for it.
Based on writer Charlie Kaufman's struggle to adapt the best-selling book "The Orchid Thief" by Susan Orlean. Kaufman quickly got into a writer's block, since the book lacked the dramatic structure needed for a movie. So he decided to write a screenplay about himself struggling to write a book adaptation, exaggerating many of the story elements and characters, and making up new ones (such as a non-existent twin brother, Donald Kaufman.) Knowing that the producers would reject the idea, he did not tell them about the new direction he was taking the story in, and simply handed in the finished script. Although this move was supported by Spike Jonze, Kaufman himself believed it would end his career (it didn't).
Charlie Kaufman was nominated for a Golden Globe with Donald Kaufman, despite being a fictional character. They were also both nominated for an Academy Award and the Academy made it known that, in the event of a victory, the two brothers would have to share one statue.
In one scene, Charlie comes home and checks his mail. He is in front of a mirror, and Donald is talking to him behind him. The reflection of fictitious Charlie Kaufman in the mirror is actually the real Charlie Kaufman.
Joaquin Phoenix auditioned for the role of John Laroche and got close to getting the part. According to Spike Jonze, during one of their final meetings, Phoenix told him that he was wrong for the part and that it should go to someone else, and took himself out of the running. Chris Cooper eventually got the part, and ended up winning an Oscar for his performance.
In his renowned screenwriters seminars, Robert McKee now makes note that he is not against the use of voice-over narration, "despite what Charlie Kaufman says." His point is voice-over narration must add to the story, not describe what's already being seen on the screen, otherwise there's no reason for it.
To portray John La Roche, Chris Cooper grew out his hair, shed weight and used a prosthesis to create the illusion of a toothless mouth. Director Spike Jonze granted Cooper's request for numerous takes so he could find the right tone for the eccentric character.
Nicolas Cage was given completely separate credits for Charlie Kaufman and Donald Kaufman. The credits were given in order of appearance and each of Cage's credits appeared in the order that Charlie and Donald appeared.
A paragraph from Charlie Kaufman's script "The Three" is shown at the very end of the credits. It reads: "We're all one thing, Lieutenant. That's what I've come to realize. Like cells in a body. 'Cept we can't see the body. The way fish can't see the ocean. And so we envy each other. Hurt each other. Hate each other. How silly is that? A heart cell hating a lung cell." - Cassie from THE THREE. There is a theory that claims that this paragraph actually reveals the hidden meaning of the film. That Donald, Susan and Charlie are "The Three" and are all actually the same guy.
The "filmography" link in the DVD includes a page for the fictional Donald Kaufman, listing his works as "Adaptation" and "The Three". There is a hidden link in the DVD main page. Scroll up from the main set of links and there is a telephone icon which appears, linking to a page with an "Adaptation Answering Machine" phone number, which had an answering machine with a message to leave your comments. Unfortunately, that phone number is no longer active.
The church mentioned by Amelia at the end of the film is the Sedlec Ossuary located in Kutna Hora, Czech Republic. About 40,000 bones are arranged to form decorations, including chandeliers in the church. This is the same ossuary that Jan Svankmajer filmed for his short film Kostnice (1970).
The book-on-tape, which is playing in the background of the orchid thief's van as Susan and John drive, is shown on the dashboard momentarily. It appears to be "The Writings of Charles Darwin, as read by Brian O'Kelley". There is no such book, no such audio tape. Brian O'Kelley is the assistant director of this movie.
When Charlie Kaufman won the Bafta in 2003 for Best Adapted Screenplay, he was unable to attend the ceremony, and Meryl Streep accepted the award on his behalf, reading out a speech he had faxed. Instead of saying, "I would like to thank Spike Jonze", she said, "I would like to spank..." and the audience applauded wildly.
Nicolas Cage earned himself just his second Oscar Nomination for this film, his first being for his role as a suicidal alcoholic in Mike Figgis' "Leaving Las Vegas" (for which he won that oscar) where Nic Cage' character is also a screenwriter.
Donald refers to "Flowers for Algernon" as a film about flowers (although Donald admits that he had never seen the film). Charlie tells Donald that "Flowers for Algernon" was neither about flowers nor a film. While Charlie is completely right that "Flowers for Algernon" is not about flowers, he is only technically correct that it is not a movie; when the novel was adapted into a film in 1968, it was retitled Charly (1968). Cliff Robertson won an Academy Award for Best Actor for playing the title character. A TV remake of Flowers for Algernon (2000) was made 30 years later.
The tropical fish species that John refers to while riding in the van with Susan are Anisotremus virginicus, Holacanthus ciliaris, and Chaetadon capistratus or the porkfish, queen angelfish, and foureye butterflyfish respectively.
The trivia item below may give away important plot points.
The credits include Donald Kaufman as the co-writer. He is also featured as a character in the movie, and the movie is dedicated "In loving memory" of Donald (at the end of the credits). But Donald is just a fictional character himself.