Visible crew/equipment: In the opening shot, as the camera moves down the building, in the windows you can clearly see the cameraman & camera on the hoist/crane. (00:01:00)
Other mistake: In the opening scene, as the camera pans down on the ladies folding sweaters in Bloomingdales, the reflection in the window shows people across the street dressed in summer clothes. (00:01:25)
Continuity mistake: When Jonathan and Sara are having drinks at the coffee shop Serendipity, the multiple straws in their drinks keep changing position. (00:04:35)
Continuity mistake: Near the beginning of their "interaction" together, Jonathan leaves his scarf at the restaurant. When they both go back, Sara puts the scarf on him and between shots it switches positions. (00:08:20)
Continuity mistake: In one of the ice skating rink scenes, the camera looks at John Cusack and there is no snow falling. It then cuts to Kate Beckinsale and it is snowing heavily. (00:09:25)
Factual error: In the final flight scene, where Sara prepares to board a plane to fly back to San Fran from NY, we see the outside of a Boeing 747. On the inside, we see a DC-9 interior (a 747 would usually have a 3-4-3 seating configuration instead of the 2-3 configuration of a DC-9). (00:11:40)
Continuity mistake: The phone number Sara writes on Jonathan's back is different than the one she writes in the book. (00:11:50 - 01:04:50)
Factual error: John Cusack enters a cab and asks to go to the New York Times offices on 42nd street. The Times is on 43rd Street. (00:28:00)
Continuity mistake: When John Cusack is trying to persuade Eugene Levy to give him Sara's details, the camera angle is cutting from one to the other. In one sequence, when we see John Cusack, Eugene Levy is clearly smiling (reverse angle), but from the front shot he's looking very serious. (00:37:25)
Continuity mistake: When Sara is showing Eve the airplane tickets to New York, in one shot Eve grabs one of the tickets and Sara holds on to the other. In the next shot, Eve has both of the tickets. And in the third shot, they each have one again. (00:42:05)
Continuity mistake: When Sara and her best friend are celebrating her birthday, a little cake is brought in and placed before them. The cake originally has one candle on it. In the next shot the candle disappears and never comes back. (00:55:20)
Continuity mistake: Towards the end of the movie, Sara (Kate Beckinsale) runs to the Waldorf-Astoria to stop Jonathon's (John Cusack) wedding. The first time she turns to leave the room where the wedding was to be held, she has just a few drops of sweat showing through her blouse. The second time she turns to leave the room, her back is drenched in sweat. (01:15:15)
Continuity mistake: At the end of the movie where Jonathan is laying down on the skating rink with all the people skating around him, it starts to snow, and you can see several small puddles all over the rink. The shot flashes to show him still lying in the exact same spot with no skaters anywhere (to signify a time lapse), but all of the puddles look exactly the same, haven't changed a bit. If people were still skating they probably would have enlarged, and if they'd stopped they should have refrozen. (01:21:45)
Factual error: Jonathan is lying in the middle of the skating rink when the second cashmere glove falls upon him. Looking around, he notices Sarah at the edge of the rink. Despite Sarah being a female and the fact that it is snowing, even Nolan Ryan would have a difficult time throwing something as light as cashmere that distance. (01:22:05)
Visible crew/equipment: In the second before last scene (when John and Kate finally met and are hugging each other in the center of the ice rink), the camera moves around them in a loop and at one point in the background, we can see the snow being shot out of the snow-making machine located just outside the rink. (01:24:05)
Other mistake: Why, when they are on the ice rink, and it is snowing heavily, does very little snow actually land on them, at least to start with?
Continuity mistake: Originally, the director was going to have the first meeting between Jon and Sara take place 10 years before they finally meet again, but later changed the difference to 7 years. When there is the close-up of Sara's Bloomingdale's receipt, the date printed is 1990, but for a 7 year difference, it should be 1993.
Continuity mistake: When Eve is getting into the taxi cab and says farewell to Sara, as the taxi pulls away, you can see in the background three people exiting the revolving doors of the Waldorf Hotel. The very next shot is a medium closeup of Sara watching the cab drive off, and in the background those very same three people once again exit the revolving doors of the Waldorf Hotel.
Continuity mistake: You see the same shot of New York from above twice, once at the beginning of the film and once near the end. You can tell it is the same shot because of the long truck parked diagonally across the street.
Answer: He didn't want to marry Halley anyway.