Factual error: I counted five canopic jars, one of which has the head of a lion. In ancient Egypt there were only four canopic jars - Hapi, the baboon-headed god representing north, Imseti, the human-headed god representing south, Duamutef, the jackal-headed god representing east and Qebehsenuef, the falcon-headed god representing west. None have lion heads. (00:04:20)
Trivia: Because the white nightdress Evelyn wears during the ship attack got wet, it became transparent, and had to be digitally painted white in post production. Otherwise the film would have lost its PG-13 rating.
Different eras. The movie "The Bounty" with Mel Gibson and Anthony Hopkins features an abundance of topless native island women but retained a PG rating. It would easily receive an R rating today.
Visible crew/equipment: In the scene where Rick is beating up Beni in the Egyptologist's office, as Rick throws him on the desk, there is a flash of light that has no visible source, and a metallic clink can be heard off to the right. (01:17:50)
Suggested correction: If you look closely, Rick actually knocked a lamp off the table when he throws Beni on it, and it hit the ground and popped... hence the flash of light and "clink" sound. You can briefly see it in this video at about 34 seconds in, right as Beni hits the table. It's a sort-of gold color and it's right behind Rick and Beni. Https://www.youtube.com/watch?v=dL3zacTLLJQ.
Other mistake: Evie explains that if Imotep was resurrected he'd bring with him the ten plagues of Egypt. This is followed by (in no particular order) a plague of Locusts, Flies, Water running to blood, the sun being eclipsed and a plague of boils. At the plague of boils Jonathan says 'last but not least, my favourite plague - boils and sores'. How does he know this is the last plague? Aren't there supposed to be 5 more? (01:23:10)
Suggested correction: This may be taking the dialog too literally. It may be foreshadowing, in the sense of "uh, oh, they've got us now" or Jonathan may simply be expressing the fact that he's had enough plagues now and would like it to stop please. By the way, you forgot the fire raining from the sky, so technically Imhotep did six, not five.
The fact that Evie stated specifically 10 plagues, it makes no sense for Jonathan to say "last" on the 6th one, without considering it a mistake on the parts of writers, actor, or director.
Jonathan doesn't simply say "last", but rather "last but not least" - a statement that is regularly used on things the speaker knows for a fact to be, in fact, not the actual last. Taken as a sarcastic remark it makes perfect sense in the situation.
I know he said more than just "last", but that was the keyword to point out that the mistake is in fact valid. "Last but not least", weather said sarcastically or not, is never meant to be said about something that is in fact not last. It's always said to indicate the last item is not necessary the least, such as at Christmas when the last gift remains or when the last graduating student is given his or her diploma.
Also it's a possibility that off screen there was death of livestock, lice, raining frogs and death of first born children. Just want to show which we missing and it's obvious why, as in a movie raining frogs or dying livestock isn't all that threatening to the main characters and doesn't look cool. And for the movie showing first born children die is just stupid. And lice, that's just too much like flies.
Trivia: The 1999 film was not a remake of the Boris Karloff classic, but a remake of the 1968 film McKenna's Gold which starred Gregory Peck and Omar Sharif, thinly disguised and transferred from the American southwest to the valley of the Nile.
Stupidity: When Evie's ladder moves away from the bookcases, she can easily put her hands on the top of the bookcase and ease back against it just like she was before. It wouldn't cause the domino effect because it wouldn't have enough force if she was stabilized by her hands.
Suggested correction: She was pretty terrified, trying not to lose her balance, and calling for help. Placing her hands on the bookcase would have required her to take at least one of her hands off the ladder, and she was probably scared that she might have fallen if she did that. It's not really a stupidity when a character does or doesn't do something in a moment of fear.
Plot hole: If the Medjai are supposed to be the guardians against Imhotep and sworn to make sure he never comes back to life then why weren't they in possession of the key that opened everything in the first place?
Suggested correction: Because it got lost in the centuries that passed. It's possible they don't even know every step on how the mummy can return.
Suggested correction: Why does it matter. They added a fifth. No reason after making up a lot of history and a cover to cover book instead of a scroll for us to suddenly go, hmm, they gave the ten plagues of God in the Bible to an Egyptian priest? Lions are cats. Therefore worship, plus the lioness goddess who slew through the land once. They can certainly add that and might make it a nicer play on the mummy's power and deadliness comparatively to the canopic heads and their gods.
A better excuse is the fact that the earliest found canopic jars are from the 11th dynasty (2200 BC) whilst the jars in the movie are way older than that (2700 BC) and could have represented anything they wanted and be more than 4. Someone should make a correction like that.
lionhead
There is no real excuse. It is simply an inaccuracy and the trivia section to include it as such. It certainly "does matter".