Continuity mistake: When the mummy is initiating his new slave, he offers him jewelry and shows him a sacred jar. Where did these come from? He wasn't holding them before in that same scene. (01:07:45)
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)
Continuity mistake: When Imhotep and his zombies are going after the group in the building where Evie reads to locate the other book, watch the mummy's CG mouth when he is walking in the zombie crowd, raises both hands and shouts something. You can see in that scene the CG decay shift on his face a bit.
Continuity mistake: Just out of curiosity, where did the bandage come from on Fraser's hand at the end of the movie? [He got burned by the salt acid in the deleted scene. An explanation, but given the editing, still a valid mistake.] (01:55:25)
Visible crew/equipment: When O Connell is talking about not getting mummified, Imhotep's sarcophagus comes crashing through the ceiling. On a close up shot immediatly following you can see a red wire wrapped around the box and leading up into the air which means the box was guided down so it would fall straight and flat.
Continuity mistake: When O'Connell and Evie burst in on the mummy after it has killed Burns, O'Connell aims at it with one revolver in his right hand. As the mummy advances, he suddenly has two revolvers in both hands, and before that, he has made no move to his second gun.
Factual error: The map that Jonathan and Evie found in the puzzle box, made out of papyrus, would be so brittle after 3200 years that handling it would cause it to fall apart. Lighting it on fire and beating it on a carpet would leave nothing but dust.
Continuity mistake: As the sun is rising, Hamunaptra is revealed (a literal trick of the light). However, long before the sun is fully up (let alone directly overhead), Dr. Chamberlain is seen holding an umbrella over his head, blotting out the sun which is now shining directly *down* on him.
Revealing mistake: The first night after O'Connell goes back to Hamunaptra with Evie, the camp is attacked. In one shot, when O'Connell is shooting at the attackers, he fires and then swings the gun to his right and fires again. As he swings the gun around the flare from the gun follows the nozzle as though it were, say, a spark on a birthday cake sparkler, definitely not like the spark on a gun.