During the ancient catfight scene, Nefirtiri gets knocked to the ground and the fight temporarily stops. Nefirtiri then takes off her mask with her right hand. On her right ring finger around the 3rd phalanx, you can see a band-aid wrapped around it. Band-aids obviously weren't available in that time period.
The heroes visit the temple of Philae while following Alex to the oasis, which is shown in its present state. In the 1930s, the temple was partially flooded by the old Aswan dam and was only moved to its present (dry) state by UNESCO in the 1960s.
The dirigible is equipped with a period brass carbon tetrachloride fire extinguisher, yet when Izzy Buttons is trying to put the fires out after Imhotep causes it to crash, he is clearly using a modern dry chemical extinguisher (resprayed so as not to be obviously modern) - this extinguisher was not invented for over 30 years after the film was set. In fact, the model used dates to 50+ years after the film is set.
Where the girls are fighting to entertain the court of the Pharoah, they switch to fighting with wooden poles with metal tips. When these poles are banged together, they sound like wooden poles. When they are allowed to scrape together, however, they make a metal sword sound.
When Ardeth Bay is riding in front of the Medjai waiting for the Army of Anubis, the sound of the horse's hoof-beats are clearly heard, as if the horse was on a hard surface, such as dry land. A horse's hoof-beats would not make such a sound galloping across soft sand.
While entering the oasis various groups of soldiers are identified. When Napoleon Bonaparte's soldiers are identified, they are stated to be "turn of the century". As this movie takes place in 1933, they should instead have been from the last century.
In The Mummy, the first scene of Rick O'Connell and the French foreign legion fighting the Bedouins is tagged as 1923. The next scene at the museum is "3 years later", presumably 1926. The Mummy Returns tags the first scene with the O'Connells searching for the Bracelet of Anubis as 1933. And Alex screams at his uncle when they are outside the museum he is "only 8 years old!" For him to be 8, his parents would have had to have him in 1925, possibly conceived in 1924, and Evy and Rick hadn't even met at that point.
When Evelyn first uses the key to open the chest containing the Bracelet of Anubis, the "open" position of the lock shows points of the star at 11 o'clock and 1 o'clock positions. Later when Alex does the same at the O'Connell house, the "open" position again shows star points at 11 o'clock and 1 o'clock positions. When Baltus and Lock-Nah are using a chemical in a syringe to open the chest at Imhotep's awakening ceremony, a close-up shows the star positions are already at the at 11 o'clock and 1 o'clock positions, meaning the chest was already unlocked.
When Imhotep's followers are bringing Evy into the ritual area, before she is set down, you can see her turn her head to the right in the long shot. Immediately afterward, there's a close-up of her being set down, and her head's turned to the left. After she sits up, all close-ups show her sitting up. But when we see the table she's on from Rick and Ardeth's point of view from a balcony, sometimes she's laying down flat, and other times the table appears empty.
When Rick goes to find the magic carpet, he takes the scepter from Jonathan, then Izzy locks the door, and Rick is still holding the scepter. When Rick kicks the door down he is no longer holding the scepter, and when it shoots back to him walking toward Izzy, he is again holding the scepter.
In The Mummy, Imhotep calls Evelyn Anck-Su-Namun. But in The Mummy Returns, we learn that Evelyn is Nefertiti reincarnated. The first movie was a retelling of the story from Boris Karloff's The Mummy, in which the resurrected priest Imhotep believes the girlfriend of the hero is the reincarnation of his lost princess. Apparently, the makers of The Mummy didn't anticipate its tremendous success and had to plan a sequel quickly, and the writers overlooked that aspect of the plot when preparing The Mummy Returns (note that the name of the villain in Karloff's version is spelled "Ardath Bey", and the hero in Fraser's version is spelled "Ardeth Bay" to help separate the two).
About 53 min into the movie, Imhotep is flipping an hour glass over in front of Alex. When the glass has been turned upside down, Imhotep's hand is flat with his thumb on the left side of the snake and fingers on the right side, but once he sets the hour glass down on the table, his hand has instantly flipped over to the other side of the snake, as if he was just going to pick up the hour glass.
In The Mummy the key was needed multiple times to open the Book of the Dead and the Book of Amun-Ra, but in The Mummy Returns, the Book of the Dead was opened and used many times without aid of the key.
When Rick is silhouetted against the spider web, he takes out his pistol and cocks it; it stays cocked while he investigates the tomb, then uncocks it when he thinks he's safe. An instant later, after being frightened by Alex, the pistol is cocked again.
During the competition between Nefertiri and Anck-Su-Namun, Anck-Su-Namun knocks Nefertiri to the ground, and Nefertiri has dropped her sais. In the next shot, Nefertiri jumps to her feet and has the sais in her hands without having had time to retrieve them, and there is no sound of her having picked them up.
In the Hamunaptra scene after the treasure hunters confront Hafez and his men and they draw guns, in a close-up shot, the Indian cultist holds up a Mauser C98. When it shifts to a wider shot, he's seen holding a Colt .45 pistol, and in the following close-up of the same cultist, the gun has shifted back to a Mauser C98.
During the tunnel flooding the distance of the water from Rick and Evy changes as the camera angle changes. The front camera view shows the water reaching their feet and even in front of their feet, but the camera view behind them always shows the water at least 5-10 feet behind them. When they reach the dead-end the rear view shows the water 5-10 feet behind them, but the close-up of them panicking lasts a few seconds before the water overtakes them. That's a long time if the water was just a few feet behind them and traveling as fast as it was.
When we first see Rick he is walking down a passage
holding a gun and a torch. After a while he looks round a corner to
see the passage he just walked through, but with no lighting.
Same number of columns, same sand buildup on the floor,
same amount of cobwebs on the ceiling.
When Alex breaks away the toilet on the train, we see water still flowing from the pipe. Then when the camera looks through the floor it's completely dry and no water is falling through or around the hole. Even if the water is to flow for a set duration, the floor should have been wet.
At the point where Rick kicks open the gate to Izzy's compound, the pistol in the shoulder holster under his left arm bounces out of the holster and drops. In the next scene it has magically reappeared.
During the fight in the museum, Bey is seen to kill several "bad guys" with the Thompson, in addition to those killed by O'Connell, yet as they are retreating up the stairs the view below shows no bodies lying around.
In London, Tower Bridge is eight bridges downstream from the Houses of Parliament, and St Paul's Cathedral is on the north side of the Thames between Blackfriars and Southwark bridges. The three famous landmarks are not close together.
In the first opening shot showing the London skyline at dusk.
The view is from St Paul's towards the Houses of Parliament.
To the right of frame is shown Tower Bridge, when in reality
it would be directly behind this viewing position and not visible at all.
After the Scorpion King is defeated, a puff of black smoke emerges from the top of the pyramid with his soul in it. Ardeth and the Medjai can see it up close from where they were fighting the army of Anubis. However, the pyramid was in the center of the oasis, and the oasis seemed to stretch for miles around it. Yet as far as one can see around the Medjai, it is desert.
In the first shot of the train station in Cairo, it appears that the city stretches all the way to the pyramids. They are actually located on the Giza plateau, which, at the time the story takes place, was a few miles outside the city border.
In the movie it looks like the temple complex of Karnak is surrounded by nothing but the desert. Yet even in 1933 Karnak actually stood right in the middle of the city of Luxor (ancient Thebes) and there should've been town buildings and people in the vicinity.
The Magic Carpet balloon uses rockets attached to the gondola for speed. In reality, the drag of the balloon would cause the the rocket-powered gondola to rotate vertically around the axis of the balloon itself. The gondola would spin around the balloon, and the craft would not move forward. Also, the balloon would provide so much wind resistance that the engines couldn't push it that fast. Even if the engines were powerful enough to move it that fast, the balloon would either be collapsed by air resistance or torn completely away when the engines are firing.
The peregrine falcon used by Ardeth Bay would not have been lowered to the status of a "messenger pigeon," but would have been trained, honored, and revered as hunting partners and companions in the ancient sport of Falconry. Also, being Egyptian, it's unlikely that the Medjai would be falconers. There is evidence that the nearby Assyrians were keen falconers. The Egyptians, perhaps because of their devotion to their god Horus, never took up falconry, despite their close contact with the Assyrians.
The opening caption contains the date 3067 BC, along with the voice-over saying, "Five thousand years ago...." The film then shifts to "modern" times of 1933. Clearly the film-makers intended 3067 BC to be 5,000 years prior to 1933. However, since the year before 1 BC was AD 1 (there was no year zero) the gap is actually 4,999 years. 5,000 is an approximation of 4,999. In 1933, one could say that 1830 was "100 years ago." So they didn't mean literally 5,000 years; but more "close to" 5,000 years.
(at around 1h 45 mins) Rick finally accepts that he is "some kind of sacred Medjai" after he sees multiple pictures on a stone wall of: a man with tattoo on left arm turning the "gold stick thing" into a spear and using it to kill the Scorpion King. While Rick's tattoo is on his right arm (not his left), the point is that he has the tattoo at all, especially considering what he was already told by Ardeth Bay.
When Rick, Evy, Ardeth Bay, Jonathan, and Alex are fighting the soldier mummies on the double decker bus, they begin by fighting four mummies but only eliminate three. The fourth was dealt with in a deleted scene.
The scene of Imhotep's original treachery is played a bit differently than in The Mummy. This is to show different perspectives of the scene, as eyewitnesses often differ in their memories in real life.
Jon starts driving the double-decker bus to try to escape (with his family and Ardeth) from the mummies. Once the mummies are on the bus, he does not need to keep driving. He could have stopped at any time and there would have been no high-speed turns, running cars off the road, or almost hitting people.
When the curator is walking in to the Scorpion King's tomb, he uses the bracelet of Anubis to "chase" away thousands of scarabs. When he enters the tomb itself, there are two torches lit, one on either side of the statue of the Scorpion King. Since anyone else who tried to enter the tomb would have been consumed by the scarabs, nobody would have been able to enter the tomb before the curator and light the torches.
In the museum, when Evy is firing the pistol that Rick handed her, the slide locks back after a shot, indicating that the gun is empty, yet she's still shooting, her arm is still recoiling, and the gun is still flashing.
When Rick is running with Alex to get to the temple before the sun reaches it, the sunlight is chasing them toward the temple. At sunrise the light would hit the top of the temple first, not creep up from the ground.
Near the start of the film, the Scorpion King is seen
walking in retreat to the desert with the remains of his army
after 7 years of battle.
Not so much as a scratch on him or anyone else.
However, nearly all of them have a bit of a limp.
When the water starts pouring in just after Evelyn says "drink from the Nile"
watch the shot where the henchman previously watching them runs
left to right as the water pours in right to left.
Just before the next cut, a rock falls away in the top right corner,
revealing the bright sunshine of the world outside the set.
Subsequent water dumps reveal a similar bright light behind them, but not as obviously as this.
The Temple of Karnak shown in the movie shows no resemblance to the actual temple, which looks more like the Luxor Temple located just south of it. However, neither the Luxor or Karnak temples resemble the one portrayed in the film.
When Rick and Jonathan are in the bathroom, about to jump out the window while the gun is firing, you can see the window crack in place. This could not be caused by a bullet because the entire window would be gone. Apparently the director wanted to make it easier for them to break through the fake glass.
The goof items below may give away important plot points.
If Evelyn was in fact Nefertiri reincarnated, why is it that Imhotep did not recognize her in the first movie? If he was a priest of her father, he had to have seen her often and would have known what she looks like.
At the end of the movie, we see Rick holding Evelyn aboard the dirigible. Judging from the shadows they make, the sun is located to the left of the camera. Looking at the sand dunes in the background, however, indicates the sun shining from the right.
The gasbag of Izzy's airship is far too small to lift a carriage of that size. Using hydrogen gas, it would take a spherical balloon about 36 feet in diameter to lift a ton. Furthermore, at the end of the film, Izzy was using hot air (as evidenced by the burner and the open hole at the bottom of the bag), which is even less buoyant. (The gas Izzy referred to had to have been hydrogen, since helium was unavailable for airship use outside the United States until the 1950s).
At the end, when waving farewell to the horseman from the balloon, we see dozens of horse tracks where the rider was obviously milling around for numerous takes, rather than flat desert he was supposedly riding through.
When the heroes reach the temple, it is sunrise but at the end of the film, when they are sailing away in the airship, the sun is already setting. Hard to believe they spent the entire day inside the temple.