Factual error: Mel and Goldie board a ferry. A visible sign states 'Detroit-Racine Ferry'. Detroit is on the east side of the state of Michigan but Racine, Wisconsin is west of Michigan, across Lake Michigan. The only water route to get from Detroit to Racine would be to circumnavigate the entire state of Michigan.
Revealing mistake: When Bela Lugosi walks off screen, it's obviously a freeze frame. The swaying tree stops moving and even though he was hit by a car, his shadow is still visible. (00:07:55)
Continuity mistake: When Nick is sitting on the bed talking to Jessica, her position changes from lying on her side to lying on her back, as the camera angle changes.
Continuity mistake: Daniels' face gets splattered with blood, in a following shot there's slightly less blood, then when she uses the radio to call back the others, her face on the screen shows no blood at all. In the other shots after it's there again.
Continuity mistake: Before Tony leaves he closes the drapes. He then says he won't go out and will stay home. She says to go out, and he agrees, so he goes to the drapes and closes them again.
Visible crew/equipment: When Dennis Weaver is in the cafe a shadow of a cameraman is cast across the table he is sitting at. The shot then changes to a wider angle to reveal that there isn't anyone near him who could have cast that shadow.
Factual error: A map in the office of Policeman Pierce Brosnan showing the "Hillside Lake" is Lake Constance (Bodensee) in the south of Germany. (01:11:00)
Revealing mistake: Before Paxton is hit with the 3 prong instrument, you can see the bloody holes already on his shirt. (01:01:20)
Revealing mistake: When the new Pope is announced, the New York Times headline is shown, and 'Copyright 1990 The New York Times' is visible. The event took place in 1979.
Revealing mistake: On the ice the tank is firing - in slow motion we see empty shells are littering the area. The shells have crimped ends, revealing them to be blanks.
Revealing mistake: When the kids are burying Gus, his supposedly dead face flinches when they shovel dirt on him.
Factual error: The movie takes place during the 1990s, but throughout the movie cars are shown with Illinois license plates with "Illinois" written in cursive. These plates were not introduced until 2001. (00:24:45)
Continuity mistake: On the ship, Dr. Zimsky reveals that project DESTINI is an acronym and that the last letter is "I" and not "Y." (INI standing for INItiative). When Rat is at his computer, he goes to the website for Project Destiny, with a "Y" and not an "I." This same thing happens when the Project Destiny subtitle flashes across the screen.
Continuity mistake: When surrounded by police and a garbage truck, Frank drives his car from the overpass onto the passing transport trailer below, then lands behind a hatchback and in front of two cars - a white compact with a sunroof and a grey hatchback. In one specific shot from atop the trailer, as Frank rolls his window down (before he requests the gun) the only vehicle behind Frank's car is the white compact, which is at the trailer's rear. Note things such as the trailer's safety bars, and the view through the compact's windshield for starters. That grey hatchback is back when the ramp is lowered, for the ensuing crashes. (00:08:20)
Continuity mistake: When Eliot Ness is at Jim Malone's house for the first time, Malone's collar is opened, then buttoned, then open again.
Revealing mistake: When Sonny is punching Carlo under the spraying fire hydrant, he misses an audible punch by at least six inches. (01:43:30)
Continuity mistake: Towards the end, Denzel drives his car into 2 cars trying to get Ethan off the hood. After that scene ends you see Denzel driving the same car and the front and rear of the car look nothing like they did when he was crashing into the cars.
Character mistake: There is no way on earth that a police officer would shoot a hostage in the thigh to 'take them out of the equation'. Anyone who suggested such a thing would likely be taken out and shot themselves. Bullet wounds to the thigh are often fatal, as an injury to the femoral artery causes massive and frequently unstoppable blood loss. Breaking the femur often leads to fat embolisms as bone marrow gets into the bloodstream and then to the lungs. In fact a broken femur is a life threatening injury in itself, and a shattered femur - a typical bullet injury - would almost always result in a total amputation. You cannot aim carefully enough to avoid the bone or artery as their position in the body varies, (as will the bullet trajectory upon impact). Jack is an experienced cop and would know the potentially disastrous consequences of shooting someone in the thigh. He'd shoot him in the foot. (00:21:05)
Other mistake: The first time the cops come to the house, Connie and her son see them from the upstairs window, and start walking downstairs. It then cuts to the cops in the living room looking around, and Connie walks in and introduces herself. Her husband is not home, so did the cops just walk into in the house without knocking?
Suggested correction: I'm pretty sure the housekeeper let them in if you listen carefully.
Continuity mistake: When Magneto lands the Golden Gate Bridge on the island, as it hits land it is still very light. When the Brotherhood start to walk toward the island, it cuts to a wide shot of them still walking on the bridge, and it's suddenly dark.