Continuity mistake: When Rob gets back to his apartment, when he places Marie deSalle's CD into his CD player, the second track reads "Patsy Cline Times Two," as it is called in the Nick Hornby novel. Much later on in the movie, when Rob meets Barry, Dick, and Marie for a drink, Marie comments, "You know that song I play, 'Earth Kitt Times Two?'" in response to Rob mentioning that he left his apartment to let Laura move out more of her stuff. (00:25:45 - 00:57:45)
Continuity mistake: For Chicagoan "L" riders: At one point in the film, John Cusack is riding the CTA, or the "L", train and speaking to the camera. He is shown walking up the steps to the platform to board the train. He boards a Purple train (you can tell from the banner in the window). After he is seated, out the window you can see the Graceland cemetery, which is north of the station in which he boarded the train, but because of where the cemetery is shown, the train can be determined to be heading south. The scene ends showing the train going underground to the subway. Purple L's do not switch to the underground tracks. So Cusack either magically transferred trains (if possible, I'd like to know how) or the L decided to change its route for unlucky John. (00:40:10 - 00:41:20)
Continuity mistake: When Laura asks John Cusack to leave, while she packs up, check out the top button on his shirt. It keeps changing from buttoned to unbuttoned several times throughout the scene. (00:55:30)
Continuity mistake: When John Cusack is on the phone to Catherine Zeta Jones he enquires about her marital status. When she responds she is holding the phone in her left hand with a large ring on her ring finger. Cutting away and then back the phone is now in her right hand but the ring has jumped to the ring finger on that hand also. There is now no ring on her left hand. (01:08:15)
Continuity mistake: When John Cusack is at a house after the funeral, he is standing in front of a fireplace. You can see the boom microphone dip into the top of the screen above his head.
Continuity mistake: When John Cusack is leaving Laura's mom's house after the funeral, all the blinds are shut, but you can see through the shade over his shoulder as he leaves that daylight is shining through. But when he steps outside it is completely dark and raining.
Continuity mistake: Towards the end when John and Joan Cusack are arguing at the wake, in wide shots John is quite far from Joan, but in closer shots their faces are much closer together.
