In the Martians' first attack a media van is knocked over, but somehow is soon upright again.
When General Casey arrives at the landing site in Pahrump, NV, there are only about 100-200 civilians and a few reporters present, but when Barbara is overlooking the landing site on the hill, the site is filled with several thousand people.
General Decker hands the President a clipboard, which reverses itself when the President accepts it.
When the Martians land at the Capitol, the trees at first have no leaves on them, then they have many leaves on them.
When General Decker says that they have to attack the Martians with nuclear weapons and shouts "We have to strike now, sir! Annihilate! Kill! Kill! Kill!!" and the President responds by screaming "SHUT UP! SHUT UP! SHUT UP!", you can see Decker's clipboard change places from under his arm to the desk and back again.
The Easter Island stone heads face in toward land, not out to sea as in the film.
During the Martians' attacks in the Nevada desert and outside the Capitol, there are several tanks. One of them is a Soviet tank, likely a T-55 or T-62, which the U.S. Army has never used. They can be distinguished by the more rounded turret.
None of the soldiers who meet General Casey in the Nevada desert ever render him proper military honors; for example, none of them salute him as he arrives.
When President Dale's daughter, Taffy, awards the Congressional Medal of Honor to Grandma Florence Norris and Richie Norris, they are not actual Medals of Honor. The sash that goes over the neck on an actual Medal of Honor recipient is blue with white stars, while the sash shown in the film is solid blue.
Just before General Decker is miniaturized by a Martian shrinking ray gun and then killed by being stomped on by the Martian Leader, there are several world clocks on view in the War Room. There is a time difference of five hours between London and New York, not six as shown.
The shape of the President's tie changes several times during his "Little people... why can't we all just... get along?" speech to the Martian Leader. This is an in-joke reference to a similar continuity error with Jack Nicholson in the film A Few Good Men (1992).
Certain examples of technology, weapons, design, fashion, etc., create contradictory clues which place the setting anywhere between 1951 and 1996. Producer/director Tim Burton did this deliberately to make the film timely and hip, while simultaneously providing plenty of retro nostalgia.
When Professor Donald Kessler and Jerry Ross, the White House Press Secretary, enter the Oval Office to tell the President that the Martians have issued a formal apology, no ceiling is seen in the previous room (i.e., set).
When Cedric and Neville Williams leave their video game that they were playing to talk to their dad on the phone, the game continues to rack up points.
When the General is firing two 1911A1 pistols at the Martian Ambassador, you can see that the slide locks in place on the pistol in his left hand, yet he continues to fire an empty firearm.
When the Martians break into the President's compound, you can see where the door is going to split before it is even blown open.
Just before the Martians' attack on Washington D.C., a Martian spaceship blows up an airplane flying by the Washington Monument. The plane is supposed to be far away from the Washington Monument and flying behind it, but as the plane flies towards the camera, it flies in front of the Washington Monument, making the plane look incredibly tiny when it should have passed behind it.
When the "Martian Girl" is standing at the foot of the President's bed, the Martian removes the headpiece of his disguise before discarding it on the floor. Just as he starts to drop the headpiece, the eyes of the now-supposedly inanimate head shift from looking ahead to looking down at the floor.
When Professor Donald Kessler's severed but still-alive head wakes up inside the Martian spaceship and inside a machine keeping him alive, a steady heartbeat is heard. However, when the camera pans out to reveal Kessler's isolated heart to the left of the screen which is also being kept alive by a similar machine, the heart is beating much faster than the speed that the audio is beating.
The Rude Gambler comes face to face with a Martian who raises his ray gun, then there is the sound of it being 'cocked'. This sound was never heard when the ray guns were used at any other point in the film.
On the world map behind the President's desk in the War Room, North island of New Zealand is missing and Iceland is rotated in position 90 degrees clockwise.
The "Martian Girl" is standing in front of the Washington Monument when Jerry Ross, the White House Press Secretary, drives up in his limousine and offers to show her around the White House, which is just across the street. Actually, the Washington Monument and the White House are about half a mile apart.
When the Houses of Parliament are shown during the Martian attack, they are shown in reverse. The tower with Big Ben is to the left of the screen when, in fact, it would be to the right of the screen, as the shot is from the south bank of the River Thames.
In one of the Kansas scenes in the film, the camera pans across the farm and surrounding areas. The faint skyline of the University of Kansas (in Lawrence) can be seen, though the scene apparently takes place elsewhere.
In the establishing captioned shot of New York City around 09:20, the orange Staten Island Ferry shouldn't pass in front of the World Trade Center towers, which were by the Hudson River over half a mile upstream from Battery Park. The ferry terminal is hidden beyond the park greenery on the far right, and the route goes even further right off-screen.
Thousands of Martian spaceships depart from Mars in the initial invasion, yet the tactics start off by landing one spaceship at a time in different locations, where they conduct nuisance raids. Although they send in spaceships en masse later, it seems that very little of the original invasion fleet ever reaches Earth.
Richie Norris brings home donuts to his family's trailer. His mother, Sue Ann, asks how old they are, to which he says "Monday" and she retorts "That's six days ago," making it Sunday, yet the film's opening scene says it is Thursday morning.
The caption of the President's press conference indicates that it occurs in the afternoon, but the President says "Good morning".
Professor Donald Kessler inspects a dead Martian and states that they have no genitals, yet several Martians are seen in their spaceships wearing "Speedo"-style briefs.