After refusing to speak about his motivations for writing Misery for two decades, Stephen King finally came out and stated that it is indeed about his battle with substance abuse. Kathy Bates' character is a representation of his dependency on drugs and what it did to his body - making him feel alone, separated from everything, while hobbling any attempts he made at escape. In his statement he said he didn't come out with it at the time because he wasn't ready and because he was afraid it would detract from the story.
Stephen King was quite impressed with Kathy Bates's performance in this film, so much so that he later wrote two more roles for her. The title role in his novel Dolores Claiborne (1995) was written with Bates in mind. King also wrote the script for The Stand (1994). His original novel featured a (male) character named Ray Flowers. Upon hearing that Bates wanted to be involved in the mini-series, King re-wrote the part as a woman, just so Bates could play the part.
In the original idea for the novel "Misery", Annie planned to kill Paul Sheldon by feeding him to Misery the Pig, and take his skin to bind the book he's written. The title would have been The Annie Wilkes 1st Edition.
According to the director Rob Reiner, Annie Wilkes' killing spree is loosely based on that of Genene Jones, a nurse who is believed to have killed as many as 50 children who were in her care over a two-year period.
Stephen King was initially reluctant to sell the film rights to "Misery" because he was skeptical that a Hollywood studio would make a movie faithful to his vision. However, King was impressed with one adaptation of his works, Rob Reiner's Stand by Me (1986), and agreed to sell "Misery" under the proviso that Reiner would either produce or direct the film.
Stephen King had originally planned to release the novel under his pseudonym, Richard Bachman. While writing it, however, it was discovered that King was Bachman. King subsequently published the novel under his real name, and announced that Bachman had died from "cancer of the pseudonym."
In a recent interview with Melvyn Bragg, William Goldman revealed that few actors wanted the role of Paul Sheldon because Annie Wilkes overshadowed him so much as a character. Warren Beatty commented before declining that the hobbling scene made Paul Sheldon "a loser for the rest of the film". Goldman was determined to keep that scene in the film as it was his favorite from the Stephen King novel.
In the movie, Annie forces Paul to burn his manuscript which is "untitled" (as seen in the closeup). In the novel, Paul titles it "Fast Cars" and is a story reminiscent of 1950s detective dramas and 180 degrees away from the Victorian Era set "Misery" novels that made him famous.
When Paul's car is found he is assumed dead, in a subplot original to the film. Coincidentally, on June 19, 1999 author Stephen King was hit by a car with some initial reports saying he had died. King eventually incorporated the accident into his book "The Dark Tower VII: The Dark Tower," which also briefly mentioned Annie Wilkes.
Kathy Bates ended up getting upset over the violence. Caan recalled that his co-star was crying when it came time to shoot that infamous scene. Bates also cried before shooting the fight sequence at the end.
In 2015 the movie was adapted to a play starring Bruce Willis and Laurie Metcalf. 16 years before, in 1999, Ramón Langa, famous for being the Spanish Bruce Willis official dubber, starred on a theater adaptation alongside Beatriz Carvajal.
The trivia items below may give away important plot points.
Kathy Bates reportedly was disappointed that a scene was cut in which she kills a young police officer by rolling over him repeatedly with a lawnmower. Director Rob Reiner was afraid that the audience would laugh at it.
Annie (Kathy Bates) places a wooden block between Paul's (James Caan) ankles and uses a sledgehammer to "hobble" him. In the book written by Stephen King Annie cuts his left foot off with an ax. The scene was changed so that there wasn't too much gore.
In Stephen King's novel "Misery", Annie cuts off Paul's foot to prevent him from escaping. Screenwriter William Goldman has stated that the reason he decided to adapt the book to film was because of this gruesome scene and the effect it would have on the audience. However, Rob Reiner and Andrew Scheinman's script revision changed the method of torture to Paul getting his ankles broken with a sledgehammer. Goldman was opposed to the change until viewing the film.
When Annie demands that Paul burn his manuscript, she lights the paper and we see a close-up of the words on the paper, an article about Cameron Crowe and how he is an amazing scriptwriter. It talks about his movies, but mostly offers praise for Say Anything... (1989).