Continuity: When Joe Fox is making martinis for himself and his father, he puts an olive in the second glass twice (but there are not two olives in the glass).
Continuity: When Joe and Kathleen are sitting at the sidewalk cafe, a woman pushing an orange shopping cart passes by twice.
Audio/visual unsynchronized: When logging on to AOL, the monitor's on-screen display doesn't correspond to the sound of the connection being made.
Continuity: When Annabelle throws the rings on the bottle, he gives her a pink one and she throws a pink one, but a green one lands on the bottle.
Continuity: When Kathleen leaves Joe on the street to get ready to meet NY152, she is wearing a wristwatch. It disappears when she arrives at her apartment.
Continuity: The clock behind the counter in Kathleen's store reads exactly 4:30 through the entire 2 minutes plus when Joe is purchasing the books. It shows different times in other scenes, so it's not stopped.
Continuity: The position of the hat on Kathleen's head when she is reading the stories.
Continuity: When Kathleen is in the cafe waiting for NY152 to show up she rearranges the book and flower and ends up putting the flower inside the book, then Joe comes in and she picks up the book to cover her face and the flower is now on top of it and the book is in a different position.
Continuity: At the dinner party, when Kathleen confronts Joe about his identity, the food on his plate keeps changing.
Continuity: When Kathleen writes the email to Joe about how she just told off someone at the café, (turns out to be Joe, but she doesn't know yet), Joe reads the email and then logs off. You hear the AOL voice say "Goodbye.", so when he finally decides to reply to her email, he just begins typing the email, without logging back on.
Factual errors: Joe Fox's explanation of The Godfather (1972)'s significance would have been greeted with a "You have exceeded the send limit" error.
Errors made by characters (possibly deliberate errors by the filmmakers): When Kathleen goes to Starbucks and orders a Tall Caramel Macchiato, the employee actually gives her a Grande cup.
Revealing mistakes: Toward the end of the movie, Joe and Kathleen are standing at a hot dog stand by a window. To avoid reflections/glare there is no glass in the window, which would be fine except that the glass is present in adjacent panes and the reflections of passers-by come and go as they walk along the street.
Continuity: When frank is typing on his new typewriter and calls Kathleen a "lone reed", the carriage stops halfway as he is typing the second line and does not move even though Frank is still typing.
Continuity: When Kathleen is waiting to meet NY152 for the first time and Joe walks in, he puts his coat over the back of the chair twice.
Errors made by characters (possibly deliberate errors by the filmmakers): It is shown several times that a key is needed to get into Kathleen's apartment building. However, when she leaves her building to go meet NY152 for the final time, she does not have her keys (and no purse or pockets).
Continuity: When Joe comes to visit Kathleen at her apartment when she is sick, he tells her to sit down at the table. When she sits down, there is a large pile of tissues on the table, but in later shots, they are gone.
Continuity: At a party where Kathleen realizes that Joe is in fact Joe Fox she is talking to him as he helps himself to the caviar garnish from a plate. He scrapes a section of the garnish from around the edge of the plate. When he does this again a moment, later the caviar garnish is intact.
Factual errors: When Joe fox is in the shop around the corner the "open/closed" sign is facing "open" side in thus "closed" side out.
Errors made by characters (possibly deliberate errors by the filmmakers): When Joe and Patricia get stuck in the elevator, the elevator man suggests they all jump up to trick the elevator into thinking no one is inside so the doors will open. Yet you know from their entry on the ground floor (and earlier scenes) that the elevator doors are operated BY HAND, and by that same elevator man.
Continuity: In the final scene at the 91st St gardens, when Kathleen and Joe kiss, a hot dog vendor behind them opens up his umbrella fully, and it is open for the rest of this kiss. A second later, as the film cuts to the dolly/crane shoot pull-away, the vendor is again opening his umbrella.
Continuity: Towards the beginning of the movie when Joe and Patricia are in their apartment (she's making coffee and Joe is sitting at the kitchen table), Joe finishes off his glass of orange juice, but when he sets it down, it is full again.
Continuity: During the scene when the staff of the store are selling off items prior to the closing, Kathleen puts a blue toy in the customers bag twice.
Errors made by characters (possibly deliberate errors by the filmmakers): When Joe is buying books for the children, the total is $73. He hands one bill over the counter to pay, then turns and leaves without receiving any change, and without anyone attempting to give him change.
Continuity: When Joe visits sick Kathleen, and she sits at the table while he fills the vase for the flowers, the table runner is alternately straight/wrinkled at the furthest end from her.
Revealing mistakes: When Kathleen is telling Joe he will love Pride and Prejudice and he is trying to read it, it clearly shows the Colin Firth cover. When Joe picks up the book Kathleen has brought at the café and says 'Pride and Prejudice, I bet you just love this book', it is actually the cover of Austen's Persuasion.