Revealing mistake: Most of the posed, fake displays in the ape's Museum of Natural History contain real people who are slightly moving if one pays careful attention. Especially noticeable are those posing with objects held in - or above - their hands.
Character mistake: When Lisa is taken to the hospital, she tells Kathy that she saw the ghost of Jodie DeFeo. The name of both of the DeFeo's daughters wasn't Jodie. Their names were Dawn and Allison. Jodie was the name of a demonic pig that the Lutz's daughter Missy had befriended.
Suggested correction: While this is true in the original novel, the writers chose to change it to the DeFeo's daughter's name in the movie. Creative license doesn't count as a mistake.
Other mistake: After they take off from California, Kirk gives a heading to Alaska. He then tells Sulu "full impulse power", and Sulu says "aye, ETA 12 minutes." Full impulse is 1/4 the speed of light. No way they would use speeds like that to go a few thousand miles.
Continuity mistake: When Christine is fixing herself after the guys smashed her up, her front end is shown to be perfectly straight for its entire width and the hood is missing. Near the end of the scene, the front end is shown crushed and unfolds again, and the hood appears from nowhere.
Revealing mistake: Throughout the film, the base station radio is not connected to an antenna. In many lengthy shots of the back of the radio we can see the power cord trailing out the back of the unit, but there is nothing plugged in to the antenna socket. This is especially annoying because base station radio problems are a key plot point.
Factual error: While the Leonov has a centrifugal section to simulate gravity, the ship's bridge is not part of it (evidenced by the stationary views outside its portholes). Yet in various scenes, including the one when Floyd rushes in to discuss his plan to return to Earth sooner with Tanya, gravity seems quite evident. Floyd marches across the compartment onto the raised pilot area's floor, then steps down from it, his foot landing audibly. Tanya's open jacket also hangs down normally as she moves about. Yet when Floyd demonstrates his plan using two pens, they float in mid air. (01:26:50)
Continuity mistake: In Maney Gault's first scene, the porch he is lying on loses a screen covering for the closeup, only to regain it for the third shot.
Factual error: During the scene where everyone runs outside, the Statue of Liberty head crashes into the street. The head is scaled too small and its size can be compared to the people taking pictures. In real life the statue head is large enough for people to walk into (17' from chin to cranium).
Plot hole: The first time they communicate with the "entity" in the spaceship, they find a correspondence between numbers sent by the entity and letters of the alphabet. The entity presents itself as "Jerry". Later on, the entity tells Dustin Hoffman, "Stop calling me Jerry" - and then Dustin Hoffman realizes that the number-letter correspondence was wrong, and the actual name of the entity was "Harry". But if that is true, how could they have communicated without problems before? The very first word that the entity used was "hello", which would have to be displayed wrong, since it begins with an "h" and has an "e".
Factual error: During the plane ride into France, the Paratroopers are holding/carrying their weapons by their sides. In reality, their weapons (M1 Garands, B.A.R.s, etc.) would be carried in special "bags" strapped to their parachute harness. This not only protected their weapons, but also secured them to their person.
Factual error: The picture of Eddie and Teddy on the road with dad, supposedly taken in 1906, shows a Ringling Bros and Barnum & Bailey circus poster. In 1906, the Ringling Brothers circus and the Barnum & Bailey circus were two separate circuses playing in different parts of the country. They did not combine the two shows until 1919. (00:27:00)
Other mistake: After the post-bank robbery shootout, a TV reporter is heard describing the shootout as taking place in a "small southland neighborhood." But earlier one of the detectives was heard ordering road blocks at Flower and Figueroa, meaning the gun battle occurred in Downtown Los Angeles. Hardly a small neighborhood.
Continuity mistake: During the early part of the movie, there are a number of references to the Blackhawk crew, yet the wreckage is that of a Huey.
Factual error: Ben, Abigail and Riley arrive at the Library of Congress to take the President's Book very late at night. However the Library of Congress, despite being shown as open, consistently closes at 5 PM.
Continuity mistake: In the beginning of the movie during the skateboard scene with Shaggy and Scooby riding along the conveyor belt, Scooby grabs a hook and both Shaggy and Scooby jump off of the skateboard. You see the skateboard falling off the conveyor belt, but in the next scene it is on the conveyor belt and being crushed. (00:03:20)
Continuity mistake: When Mulder and Scully start frantically running from the bees inside the dome Scully is clearly seen untying her belt twice. (01:01:55)
Other mistake: During the scene where the Japanese are being rounded up and taken to the internment camp, the camera is panning over the crowds of people walking down the street. Half way through this scene, there is a woman and a little girl, who seems to be carrying a stuffed Elmo, hardly appropriate for the time period.
Plot hole: Det. Kerry says at the scene of Paul's trap, "He had two hours." There is no way she could have known that. The clock simply said 3:00 and the tape specifically says "you have until 3 o'clock or this room will become your tomb". No way to know that's two hours after the fact. (00:17:30)
Suggested correction: In the flashback of the razor wire trap, it shows the clock as a few minutes past 1, so he did know he had 2 hours.
Continuity mistake: When Seth has been sliced by the blade, he spits blood that goes all over his face. It then cuts to Hoffman looking at him, then back to Seth, and now the blood on his face has gone. This happens three or four times. (00:05:10)
Revealing mistake: At the end when Katie enters Hunter's room and throws Kristi against the camera, Katie's reflection in the wardrobe mirror shows her in a different position from when she attacks Kristi, to after she drops out of view.