Continuity mistake: In the scene where Jonathan picks up the scarab, it breaks open and the beetle inside starts to crawl under his skin. We see Brendan Fraser tear Jonathan's shirt and cut the beetle out of him. However, in the very next scene, we see Jonathan walking into the temple, his shirt is intact and there is no blood to be seen.
Continuity mistake: In the scene where Imhotep's priests first pop up, Jonathan is on Rick's left, and the guy in black is on his right. But in that split-second shot that shows them starting to fire, they are on the opposite sides. [In the director's commentary he does mention this but says it's because they had to cut some scenes out due to time, still a mistake but has a reason.]
Trivia: An explanation for why there is no salt acid booby-trap protecting the gold book like there was protecting the black book. In the missing scene some of Imhotep's priests burst through the floor/ground and attack Jonathan and Rick, who get tossed aside. The priests then open the gold book's hiding place and get burned all up by the salt acid. You can even see when Rick grabs the TNT that there is smoke rising from the hole.
Trivia: In the scene where Evie wakes up to find a rat on her chest she screams and rolls over and the rat then lands on the female mummy. According to the commentary on the DVD the rat wasn't meant to land on the girl playing the mummy, who was only the make-up lady. As soon as it landed on her she jumped up screaming.
Trivia: The warning that is on the chest containing the Canopic jars ('Death shall come on swift wings to whomsoever opens this chest') is a variation of the curse that was allegedly written on the walls of Tutankhamen's tomb: 'Death shall come on swift wings to him that toucheth the Pharaoh's tomb'.