Visible crew/equipment: In scene where Chris is arguing with the cops look very closely in the window of the car. The boom mic, camera, and crew are all visible.
Factual error: There is a scene where the guy takes a date whale watching in Boston Harbor. There are no whales in Boston Harbor, it's at least an hour and a half trip out to go see whales from Boston.
Factual error: When testing the new phone installation, the engineer only dialled the number, and not the area code, as you have to do on a mobile phone.
Revealing mistake: You can tell all shots in the parallel world where there is writing visible are simply regular shots being reversed because Molly Ringwald's watch and ring, which she wears on her left arm and hand, suddenly are on her right arm and hand. Especially obvious in the scene where she goes over work papers with Sandy.
Other mistake: When Jude Law and the police officer are walking to the officer's car, Jude asks the officer if he is married. Why is it he asks this? Earlier on in the film, at the police station, the officer told Jude that his wife gave him that very same necklace.
Continuity mistake: While standing in the water, the guys' bong jumps from hand to hand between the three of them without being passed.
Factual error: When Vic is beginning to fall in love with Louisa, he stays up one night reading her novel-in-progress. However, Louisa is Spanish, and it's clear from her accent that her native language is Spanish, and writers very very rarely would deliberately choose to write in their second language when they could write in their first language - so her manuscript is almost certainly in Spanish. And it's extremely unlikely that Vic speaks Spanish: he shows no signs of speaking Spanish; his character is not that bright and not that well-educated; and even if he learned it in school he's been out of it for many years and wouldn't be able to read it at that time. Even if Louisa had chosen to have her work translated so it could be read more widely, she was in the process of writing it; translation is a long, expensive, and involved process and it wouldn't have been done while the work was still being written, as we have already learned it is. Therefore, Vic would have been unable to read Louisa's work.
Factual error: When Bill and Jason are heading up to Canada (and Lucia is following in her own car), they are driving past several high mountain peaks, and up through a winding valley. Problem is, they started in South Bend, IN and are heading towards Detroit, MI, and that area of the country is notoriously flat, other than occasional hills.
Continuity mistake: Birdie and Justin are dancing to a song and when it ends the band announces, "We are going to take a short break and leave you with some fine tunes on the jukebox." The song "To make you feel my love" starts, but as they are dancing you can still see the band playing and someone singing.
Continuity mistake: After the photo shoot on the beach the characters are passing around a jug of wine that is almost empty in one shot, but each shot after that it is closer to full.
Continuity mistake: The young son of the Chinese owner of the violin is near-sighted and his glasses have concave lenses. When he attends the auction as an adult he is far-sighted with incredibly thick convex lenses.
Factual error: When the whole of the court go on the "view," it seems as though the bus includes barristers, the judge and members of the jury. In reality, the judge goes with the jury, the barristers are not allowed to.
Factual error: In the big professional Latin dance championship scene at the end of the movie, the competitors perform four dances: the samba, the cha-cha, the paso doble, and the rumba. In reality, however, a professional Latin dance championship, regardless of where you go, is almost always a 5-dance event: a cha-cha, a samba, a rumba, a paso doble, and a jive. Rumor has it that a jive sequence was originally supposed to be part of the competition scene but was cut from the final version of the film for unknown reasons.
Continuity mistake: When Frank and Martha are walking by the river, he is carrying her orange bag. At first he is carrying it hanging by a strap from his shoulder, but when the angle changes he is carrying it by a handle.
Continuity mistake: Rosina is meeting for tea the fish trader that she is supposed to marry. Her mother hands her the plate with cake, she takes it in the first shot, but she is taking it again in the following. (00:10:15)
Other mistake: Christopher Reeve's nurse has just installed the camera, and they are showing it to Daryl Hannah. During a close-up of Jason Kemp's camera displayed by a monitor, she notices that the woman victim of domestic abuse is wearing too much make-up for that time of the morning, no doubt to hide the results of the beating she took. Jason does not move the camera at that point, but a minute later he (it actually looks like she is the one doing it, but there's an engine buzz so it should be Jason operating it, not her turning it by hand) rotates it to the right. The visual in the monitor is unchanged from earlier even if the camera moved. (00:33:30 - 00:34:30)
Continuity mistake: When Lee and Chris go swimming they briskly towel off still a little wet. Yet a few moments later they're completely dry.