In the poster for the film, the Greasers are laughing as Johnny is smirking. This candid shot was taken during the photo session where the actors were supposed to look tough at the camera. What happened was that when Leif Garrett went to the table, Ralph Macchio said, "Hey, Leif, that's for the talent." This comment cracked up the cast, and the photo was used.
When Dallas falls out of his chair at the drive-in, it is entirely accidental, and Ponyboy (C. Thomas Howell) looks briefly at the camera while laughing.
Francis Ford Coppola received letters over the years from fans of the novel, many expressing disappointment that several key scenes from the book were omitted from the film version (they were in Coppola's original cut but were edited at the studio's behest). Several years later, Coppola's granddaughter was reading the book in class and was about to watch the film with her schoolmates. Feeling embarrassed, Coppola cobbled together what would eventually become his Director's Cut, "The Outsiders - The Complete Novel."
In the film, Dallas harasses Cherry, and the two have an altercation. The scene was shot early in filming, and Matt Dillon and Diane Lane recalled years later that it got them off on the wrong foot and created real tension between them off-set, which is why their irritability with each other in the scene seems very real. When the cast reunited in 2003 for the 20th Anniversary, the men laughed when Lane told them about this, all agreeing that they remembered the ongoing feud between her and Dillon. Lane blames her adolescent insecurities for being so sensitive to Dillon's teasing. She also admitted that she fondly remembers how protective he and the other boys were of her. Dillon and Lane ended up shooting two other films as each other's love interests and became good friends.
In the scene where Dally argues with a nurse in the hospital about the whereabouts of his hospital gown, the nurse is the author of "The Outsiders," S.E. Hinton.