Several pieces of dialog from background characters, such as a customer in the bar saying that Patrick has an "ass like a Skippy jar". On the director's commentary, Affleck admits that he started to worry about whether or not the extras, who really are residents of Boston, would take direction or tell them to buzz off.
On the DVD commentary, Ben Affleck says that he and Jill Quigg improvised the scene early in the movie in which Quigg (as Dottie) talks to the press about the flyers they had posted and the vigils they had planned. Affleck says that he would feed her some lines and then she would perform them; her mispronunciation of the word "vigil" as "visual" came from her mishearing what Affleck had said from behind the camera, but he later decided to keep it the way she had said it.
Too Soon: The release of Gone Baby Gone was delayed in the UK because there were parallels to the recent disappearance of Madeline Mc Cann.