Continuity: During the scene in the mall when the girl is in the dressing room, she keeps putting on more layers of clothing.  But as they are shooting different shots she will have a hot pink shirt on, then it is back on the hanger, and then back on again.  It switches back and forth many times.

Other: At the very beginning of the movie, when the guy throws the match into the house, it doesn't enter through the window. The match crashes and bounces back, but the fire inside the house still occurs.

Continuity: In the scene where Dan Akroyd's character is discussing the aliens with the military the digital clock behind him reads different numbers each time they show it.

Continuity: During one of the final scenes in a laboratory, some of the characters are talking about finding 500 gallons of selenium to help stop this evolution. When they ask, "Where are we going to find 500 gallons of Selenium at 2 o'clock in the morning?" there is sunlight coming through the trees outside the window.

Continuity: Opening scene - meteor smashing into the car and you see the windshield flying out. Next day, character is driving the car and viola the windshield is still intact.

Factual error: At the end of the film, when Duchovny and Jones are on the ladder truck shooting the head and shoulders, they are yelling "go go go". They slide down the ladder and the next shot is the fire truck speeding away. Movie elapsed time 5 seconds. It is a physical impossibility for a fully extended ladder to be lowered, retracted and bedded in a span of less than 4-7 minutes. Even if the hydraulic lines are cut, the ladder would remain upright and not collapse/retract.

Continuity: In the department store scene, on the bridge, Ira cocks the shotgun before the alien gets to him. When the bird arrives, he cocks it without firing a shot, and then shoots. A shell doesn't leave his gun when he cocks it the second time.

Factual error: When Ira is first examining the blue fluid under the microscope, he switches the objective from a lower power setting to a higher power setting, but the image does exactly the opposite - goes from a higher magnification to a lower one.

Plot hole: On the doors inside the white dome, and on the elevator door, it is marked "Vapor Lock." This is impossible due to the mine shaft opening. It can't be vapor locked when there's an opening.

Continuity: When Ira and Jones break into the secured area to get the specimens, they lay down in front of the barbed wire. Ida is wearing a black Colonel Uniform and Jones is wearing a Private Uniform. But when they get inside the facility Ida's uniform is clean and has no dust marks.

Continuity: At the start of the movie when Wayne is practicing for his firemans exam he carries the dummy through the door and knocks over a pole which lays across the doorstep and stays there, when he comes out the pole has gone.

Continuity: During many scenes of the movie, you can notice that Orlando Jones has no glass in his glasses.  In fact, when they are in court, he puts his fingers through the frame to rubs his eyes. [Some people have said they're meant to be fake in order to make him look clever, but they've definitely got glass in some scenes.]

Revealing: This film was shot in Page Arizona with is pretty far north in the "high country". When they first drive up to the meteor side, there is Saguaro cactus that are only a couple of feet high with huge arms and a neon greenish color. These only grow on the desert floor in Arizona and they certainly are not neon colored. Additionally, the arms don't start appearing until they are much taller as they grow them to balance themselves since they have a very shallow root system.

Continuity: At the beginning, when Wayne is running from the meteor, he jumps to the ground with a yellow fireman's jacket on. He then pulls himself up and only has a blue shirt, and when they show the wide view of the crater, he has the jacket on again.

Continuity: When the guy on the green is waiting for his date, the champagne bottle mysteriously changes places. When setting the bottle down the lights from above change angles when he's walking to wash off the spillage.

Continuity: At the end of the film when David Duchovny and Orlando Jones go up the ladder to squirt the Head and Shoulders into 'the hole', Orlando Jones gets sucked up into the alien and when he is pulled out he is covered in slime from head to toe, (including his glasses), as is David Duchovny. However, in the next shot of them going down the ladder there is no slime on them at all. In the next shot when they are standing at the bottom, while the truck pulls away, neither of them have much slime on them, and Orlando Jones' glasses are completely clean. The amount of slime they are covered in changes throughout the next few shots.

Factual error: The aliens are supposedly nitrogen-based, making them vulnerable to selenium in the same way humans are vulnerable to arsenic because we're carbon-based. However, nitrogen atoms don't have the valence real estate to form the long molecular chains critical to the DNA structure shared by terrestrial and alien life (when Ira first analyzes the sample, he finds DNA with 10 base pairs).

Continuity: In the scene near the end when they first drive under the thing in the fire truck and it 'passes gas' on them, Orlando's glasses disappear during the 'passing' and then reappear a couple of shots later.

Continuity: When Julienne Moore's character trips over, from the distant shot she gets up onto her hands and knees, then when her garter is seen, she is lying flat on the floor again.

Factual error: The movie is set in Arizona, and at the end they say that the army will drop the napalm at noon. Granted they go a little early, but it should still be pretty warm, but, you can clearly see their breath as they talk.