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, the director, Jeremiah S. Chechik, changed it to Sam leaving the Jack In The Box instead.
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.
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.
Benny 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.
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". MGM promptly slapped him with a $5 million lawsuit for breach of contract (which was ultimately settled out of court).
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.)
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).
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, Furgusen's. 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.
The two restaurants used in the movie, the Milk Bottle Cafe and Furgusen's, were heavily damaged in a fire on September 26, 2011. Furgusen's was a total loss but the Milk Bottle, one of two such Spokane, WA icons, survived.