In order to make it seem as if he is an inexperienced writer, Johnny Depp used his left hand in the writing sequence. Being right handed himself, using his left hand gave off the squiggly impressions of a child's writing.
During the filming of the scene where Benny rushes to Joon's aid after she is put into an ambulance, a house party was happening less than a block away from the shooting in Spokane's Peaceful Valley area (it was a day scene actually filmed at night). After hours of re-takes, Jeremiah S. Chechik bribed the local revelers with a cornucopia of food from the crew's food tent, which kept them pacified long enough to finish the scene (at around midnight).
Joon's comment to Sam, "Having a Boo Radley moment, are we?" is a reference to the character of Boo Radley in the novel "To Kill a Mockingbird", a "Boo Radley moment" is when a person is astonished at the sight of something or someone excessively strange and/or rare. Conveniently, in Spokane Washington, the city that this film takes place in, there actually is a gift shop called Boo Radleys.
Originally in the script, Sam was supposed to leave dried flowers on the porch after Joon threw him out. A hour before shooting the scene, Jeremiah S. Chechik changed it to Sam leaving the Jack In The Box instead.
First choice for the leads were Tom Hanks and Julia Roberts, followed by Tim Robbins and Susan Sarandon. Eventually MGM had their dream casting in place: Johnny Depp, Woody Harrelson and Laura Dern. Harrelson's contract would have given him top billing. When Dern (a recent Oscar nominee) found out that she would be third billed, she quit the picture. Harrelson followed soon after, having landed the young male lead in Indecent Proposal (1993). MGM promptly slapped him with a $5 million lawsuit for breach of contract (which was ultimately settled out of court).
The El Camino that Benny drives in the film was bought from a local man in Spokane, WA. For the film, they redid the entire inside and outside of the car because it was a wreck when they bought it. After filming for the movie ended, they sold the car back to the original owner.
Sam emulates Buster Keaton often in the movie. The wonderful "dancing rolls" scene is actually honouring from The Gold Rush (1925), performed by Charles Chaplin during his dream sequence to impress the dance hall girls.
The exterior of the cafe where Ruthie works (with the dancing rolls scene and others) is the Milk Bottle Cafe in Spokane, WA. Oddly enough, the interior was shot in an entirely different restaurant, Ferguson's Café. The two restaurants are actually next door to each other. Even weirder, that's not the only building shaped like a milk bottle in Spokane.
In the restaurant scene between Sam and Joon, as they are discussing raisins, Sam says, "It's a shame about raisins." This is a tongue-in-cheek reference to the video for the Lemonhead's hit, "It's a Shame about Ray," which was released the year before and in which Johnny Depp starred. (At the end of the video, Johnny can be seen carrying a curved cane almost identical to Sam's.)
The two restaurants used in the movie, the Milk Bottle Cafe and Furgusen's, were heavily damaged in a fire on September 25, 2011. Ferguson's Café was a total loss but The Milk Bottle, one of two such Spokane, WA icons, survived. Both The Milk Bottle (May) and Ferguson's Café (July) reopened in 2012. Ferguson's still features the counter where Sam danced the rolls.
In the scene where a close-up of Joon's medical bracelet is shown, the address on the bracelet is the actual address of the house in Spokane, WA that was used in the film. The house is still there (2016).
Johnny Depp wanted to watch a movie in the IMAX Theatre at the park in Spokane, WA, where they filmed the famous "troublesome hat" sequence. He unfortunately never got that opportunity. Recently, that same theatre has been under threat of demolition by city hall, and there are numerous people that take up most of the city that are trying to save it.
During the diner scene with Joon and Sam, Joon refers to raisins as "humiliated grapes". Depp also used this reference in 'Pirates of The Caribbean: Curse of The Black Pearl' during an extended/deleted scene where Jack Sparrow (Depp) is captured in the caves; He claims "parlay" then explains the word was invented by the French.