Near the beginning of the film, the T-X uses a mobile phone to track down the identities of the people she needs to kill. However if you look at the phone as she's dialing the number, you can see there's no signal on it.
Sarah Connor dies in August 1997. In accordance with her will she has many guns hidden in a coffin right after her death. After the cemetery scene, at the RV, The Terminator pulls a Heckler & Koch UMP-45 out of the coffin. This gun wasn't for sale until mid-1999, two years after the gun was placed in the coffin.
When the TX is pulled over by the police officer at the beginning of the film, the officer walks up to her in the Lexus. Just before the officer says, "Lady, do you have any idea how fast you were goin'?" we see the TX's mouth moving as though she's speaking, but we hear nothing.
The naked Terminator squeezes the stripper's hand to get his clothes, while "Macho Man" by The Village People is playing. When he walks out the front door all dressed up, after what should have been several minutes, the song on the P.A. system hasn't skipped a beat.
In the voice-over, John claims he was 13 when he was attacked by the T-1000 in Terminator 2: Judgment Day (1991), but John Connor was 10 in that movie (However Edward Furlong, the actor playing John Connor was 13 at the time of filming).
There is a reference to the Skynet computer operating at 60 "teraFLOPS per second", which is an inaccurate use of the term FLOPS (tera is correct, as it means trillion). A FLOP is an acronym for FlOating Point Operation and a FLOPS is a FlOating Point Operation per Second (note that FLOPS is singular, not plural). The FLOPS count is used to measure a computer's performance, particularly those in the scientific and academic fields. So to speak of "FLOPS per second" is redundant. One could argue that "FLOPS per second" refers to acceleration (such as miles per hour per hour) but members of the scientific computation field never speak of a computer's acceleration.
Sarah Connor's plot at the cemetery said that she was born in 1959. However, the events of The Terminator (1984) occur in May of 1984. The setting of Terminator 2: Judgment Day (1991) is ten years later and it is revealed that Sarah is 29 years old, making her 19 during the events of the first film and what would then place her birth date in 1965.
In Kate Brewster's first scene in the department store, she talks to her father on a small light-colored Nokia phone with blue-illuminated keys. She receives the message from the veterinary clinic alarm system on this same phone, most likely a Nokia 6200. But she calls 9-1-1 from the clinic van with a larger plain black phone with non-retractable antenna (most likely a Nokia 6160.)
When the Terminator and John Connor are driving the veterinary truck into town, notice the grab handles on the front door frames. In early shots the grab handles are missing the small, square, screw covers which reappear a minute later.
At the animal hospital again, when the T-101 smashes the TX through the wall with his truck, you can see briefly on the next shot that there is no driver in the truck. Moments later the T-101 appears from the door.
In some of the action shots, the hearse is shown minus both the front and rear right-hand side wheel covers; however, when the hearse comes to rest near the RV, the right-rear wheel cover has reappeared.
Inside the mausoleum, after Kate Brewster grabs the gun, the Terminator is standing with his right shoulder towards Brewster; they cut away, then immediately cut back, and his left shoulder is towards her.
During the sequence when the Terminator is in the convenience store, he is seen throwing items (bags of chips) in the basket which is nearly overflowing. After the cutaway, the items are neatly stacked in the basket.
When the Terminator is trying to shut himself off by hitting the Jeep, the tires and rims are bent out by the opening blows, yet appear upright and inflated in the next shot, and then once again bent out in the subsequent shot.
When we see Kate riding in the passenger seat of the RV, several views show only a square RV window behind her, with a flat wall forward of that. Other shots show (correctly) an angled window ahead of the square one.
The Terminator turns to open fire on the SWAT team at the cemetery twice; first when Dr. Silberman sees him (as evidenced by the visible muzzle flash from the machine gun, with no audible gunshot), and again when he actually does start shooting.
When the T-101 puts Kate in the Vet's van the first time, it pushes the tire iron through the right-hand handle and bends the end back on the left-hand handle. Later when the van is going up the on-ramp, the tire iron is reversed (the bend is now on the right-hand handle) and at the gas station, it is back to the original position.
When Kate and the Terminator are talking in the RV, when the camera is closer to the Terminator, the armrest for his right arm is down. When the camera is closer to Kate, the armrest for the Terminator's right arm is up. This change happens repeatedly.
At the AMPM petrol station in the desert, the cash register is covered with hand written signs saying the phones/computers are out of order, and thus credit cards are not working. Yet after Terminator shoplifts some food, the phone is working for the gas station attendant to call authorities.
In the mausoleum, when Kate is pointing a pistol at the Terminator, her finger is alongside the barrel. When the Terminator grabs for the pistol, it fires, hitting the Terminator in the mouth, even though Kate's finger was never on the trigger.
Before the naked Terminator seizes the clothes of the stripper the stripper is clearly wearing a leather jacket and blue jeans. When the Terminator enters outside he's wearing complete leathers including leather pants.
After John crashes into the back of the sedan, they look back to see the police coming, you can also see a red car with a damaged rear light (LHS), then moments later the crane truck crashes though the wall, the red car is not damaged and then the crane hits the red car breaking the rear light.
While the Terminator and the T-X are fighting in the bathroom, toilets, sinks and water pipes are broken; resulting in water gushing everywhere. Despite this, both the Terminator and the T-X's clothing remains dry throughout the fight.
When the Terminator and friends are in the RV in the desert, when the camera is outside the RV while it's driving, you can see blue screens covering the windows inside! As you know the blue screen is a wall for computer simulation as when an actor is in a car or truck the car never moves yet the outside world does.
Just before John Connor crashes into the car in front with the Tundra, there are a couple of shots shown from inside. During these shots, there is a cameraman visible on the extreme left hand side of the frame, hiding behind a black jaguar.
When the T-X kills Jose Barrera at the fast food restaurant, the drive through window is on the wrong side of the building. The T-X could have driven the wrong way but it was shown at the speaker, driving the direction that the drive through should have been.
The Terminator tells Kate and John that the Crystal Peak base is "north east on a bearing of 'zero point five degrees'". A bearing of 000.5° is almost exactly due north. Later Kate flies the plane on a heading of 015° ("zero one five degrees" in aviation-speak). This is different from what the T-101 had told her, and even given his mistake it is still closer to north than it is to north east.
After the crane chase, whilst the T-101 is climbing into the vet van from the roof we can see briefly down the street that there's a corner approaching as there's buildings just ahead of them. However when the T-X emerges from the rubble and looks down towards them driving off, they're now on an open road with nothing at all ahead of them.
Having control of a vehicle's computer would not allow the car to be driven remotely, as the steering is completely mechanical (even power steering), and although some modern cars have a computer controlled throttle (not the cars in the movie though), the pedal would not depress (same goes for the brakes, clutch and gears).
Firefighters are seen extinguishing a vehicle fire outdoors with a carbon dioxide fire extinguisher. These types of fire extinguishers would be ineffective on a car fire as they work by depriving the fire of oxygen. Carbon dioxide quickly disperses outdoors and the fire would have its oxygen back in no time. Firefighters use dry chemical extinguishers on minor car fires and hose lines on larger ones.
The entire chase scene with the crane ignores numerous laws of momentum, inertia and tensile strength. Using the crane arm to demolish a steel-framed building would not only completely mangle the arm, it would also cause the crane itself to crash, instead of which it doesn't even slow. Similarly, whilst the vehicle easily has sufficient mass and momentum to smash cars out of its path, having a tonne or so of metal hitting it at roughly 40mph is going to have an effect on the steering, it wouldn't just casually carry on in a straight line as if nothing happened. Most significantly, after the T-800 drops the crane's hook through the manhole cover, the hook would firstly need to actually latch onto something to create the desired effect (instead of just getting pulled right back out again and dragging along behind the crane) and whatever it anchors itself on would need to be sturdy enough to stop the tens of tonnes of crane - if a building can't do it, it's rather unlikely that a sewage pipe is going to. Even if such an item could be found, the cable would not tear through the road without slowing the crane down at all and would in all likelihood bring the crane to a much slower, more drawn-out and less visually impressive (and hence much more boring) stop.
When John Connor has broken into the Animal Hospital and then into the medical cupboard, he takes some tablets from a bottle labeled Phenobarbitone, presumably as painkillers. Later, Catherine Brewster tells him those are used to chemically neuter dogs. Both are incorrect, Phenobarbitone / tal is used to control epilepsy.
When Kate Brewster is flying the Cessna 172 with John Conner, she says they are flying at 160 mph - a C172 cruises at 115 mph. 160 mph is the Red Line or Never Exceed airspeed, this airspeed could only be reached in a dive, certainly not while in cruise (even if they were in a hurry and flying at full throttle).
In the T-X POV shot where she examines Jose Barrerra's retina and name tag, his surname on the tag is spelled differently from how it is in the T-X's POV. (This may not be an error, however, as nametags often get misprinted. Ask any employee of a cheap chain store/restaurant.)
The .30 caliber machine gun (with the drum clip) that The Terminator uses against the police outside the mausoleum is supposedly dropped before he enters the hearse. However, later we see it beside the coffin, but it is possible he turned for a moment, and tossed the weapon in beside the coffin, where we see its perforated barrel shield as he's reciting the T-X's target list, and later as he carries it to the RV.
When the casket opens in the hearse, which was first seen full of weaponry, it is now hiding John Connor. However, later on they are seen to be armed to the teeth. Look closely, and you'll see John is laying on top of the weapons. Some space made with the removal of the .30 cal MG, along with the curved upper lid, left enough space for John.
When the T-101 is holding open the Crystal Peak bunker blast door he uses one hand to hold back the TX from getting to John and then use the other hand to pull his power cell out. This did not leave an arm available to hold open the door, however the door could have stopped functioning after a while when meeting significant opposition from the terminator.
It's finally acknowledged that the T-101 (Arnold Schwarzenegger) with a skeleton of extremely durable non-identified metal would almost certainly weigh 8-10 times that of a human with similar mass. (The fireman cannot move him even slightly and states, probably literally, that "this guy weighs a ton".) So how can he drive and/or ride in cars and pickup trucks that he probably weighs more than?
In the flashback scene showing an HK flying over the water it is using a high power floodlight to look for its targets. Since it is basically a terminator, it would be equipped with infra-red like the T series and would not require an additional light source to operate at night.
In the scene at the RV, we learn that the Terminator must obey Kate Brewster's orders, as she is the one from the future who sent him back in time. However, there are several times preceding this scene in which Kate Brewster barks orders at the Terminator (i.e. "Let me go!", etc. ) and he ignores her.
In the end credits, the character of Kate's fiancé is listed as 'Scott Petersen'. Actually the character's name is Scott Mason (mentioned by the two L.A.P.D. detectives in the movie). (This was an editing goof, altered because of an event noted in the 'Trivia' section.)
When the Terminator exits the mausoleum with the casket and turns to fire at the police, the angle of the machine gun barrel as he fires is such that all bullets would hit the tree tops above the police cars rather than the cars.
When the T-X's weapon is damaged, her on screen display chooses a new weapon. The display shows the name of the weapon and a description, but if you look closely the description for all of the weapons simply states: "Important information about this weapon is being displayed here".
When Kate's fiancé (the TX) is informed of her whereabouts, the TX punches through the seat and through the agent driving the cruiser. As the officer is leaning forward in shock and dying you can see the ignition of the cruiser is in the off position.
During the crane chase, the T-X's vision/display shows the vehicles she's controlling as well as information about them. On the right side of the screen, Vehicle 2 (the fire truck) shows to be traveling at 93 mph which is extremely unlikely, if not impossible given the fact that they're on a service road traveling through a big city.
The goof items below may give away important plot points.
While in the bunker at the end of the movie, when John says "These computers are 30 years old," a Dell computer box, complete with the big blue E, is clearly visible among all the ancient computers. A modern day black Dell CRT monitor is also clearly visible on the center desk in the final bunker scenes.
Towards the end of the film, the T-X activates the robotic defenses which are presumably the first models of Terminators. In one scene later on we see through this older terminators vision and it's a sharp crystal clear image. The supposedly more recent T-101 however has a blurry red view imaging. How can a newer model have an inferior optical system?
When the good Terminator (Arnold) throws out his defective fuel cell and it explodes, he states that he has two. The second one is clearly visible next to the defective one when he removes it. To terminate the T-X at the end of the film, he removes the second fuel cell. This would leave him with apparently no power source. While terminators from the previous films were shown operating from some unspecified alternate power source, there is no evidence that this wasn't the other fuel cell. Also, as stated in the goofs for Terminator Salvation, the prior terminators must have had different power types of power sources altogether or they would have exploded violently when crushed in a hydraulic press or melted down in molten metal. Correction: The Terminators in the first two films are of a different model. They are model T-800, while in this movie it is a model T-850. They appear to be the same because all three are series T-101, which is the series that looks like Arnold. So the fuel cells must be one of the upgrades in the T-850 model terminator. It is also plausible that the design of the fuel cells have changed because of the changes to the time-line made in the films. So the terminator in the first two films are Cyberdyne Systems Model T-800 Series T-101 Terminators, and in this third film it is a Model T-850 Series T-101 Terminator.
During the scene in which the T-X infiltrates the United States Air Force's Cyber Research Systems base and manages to execute Robert Brewster just after he activates Skynet. Although the T-X has the ability to resemble anything it touches and is possibly the reason for the ease at which it entered the base. It's never explained how exactly the T-101 accompanied by a man supposedly with no current official existence, fully armed managed to get into the base. Although Kate is the daughter of Robert, there's no way at all that a secure facility would allow the entry of two heavily armed men.
When the T-X, in the guise of Scott Mason, starts driving the police detectives' car from the back seat, she is able to control the accelerator and brakes although at that point she has not (as shown with the police cars earlier and the military machines later) been seen to inject her nanotechnology controllers into the vehicle.
When the T-X shows up (posing as Kate) to assassinate Robert Brewster, before The Terminator begins shooting, the T-X begins to react like she is being shot at just a second before The Terminator starts firing.
After the Terminator shoots the fake Kate/T-X at the military base, he can be seen throwing the machine gun to the right of the screen, landing on a mattress clearly meant to protect the prop machine gun. Seconds later, when Kate runs to her dying father, the mattress is now gone and the prop gun is now on the floor.
When the T-X poses as Kate to attempt to assassinate Robert Brewster and is shot by the T-850, her "clothes" take normal bullet damage, not the mimetic "splashes" from both the T-1000 in T2 and on the T-X in earlier scenes.