The crossbow traps in the tomb scene were based in reality. According to Chinese archaeologists, the excavation of the Qin Dynasty Terracotta Army in Xi'an is progressing so slowly, partially because the site is filled with similar traps.
The filmmakers originally considered bringing back Arnold Vosloo as Imhotep, except this time, he's a last-resort ally who helps the heroes defeat the Dragon Emperor. Vosloo hated the script and didn't want to make a Mummy movie without Stephen Sommers, so he declined to return. Oded Fehr was also asked to reprise his role as Ardeth Bay. Fehr declined because Imhotep was not to be in the film, and had felt that if there was no Imhotep, then Ardeth Bay had no point or reason to appear in the movie.
Since Jet Li was only available for a part of the shoot, it was decided that the Emperor would be either a rotting mummy or encased in terracotta in most of his scenes. In that way, Li could play the Emperor in the flesh, and the remainder of his role would be done by a CGI character.
Rachel Weisz did not appear in this third installment of "The Mummy" films, and instead, her character, Evy, was played by Maria Bello. There were differing accounts as to why this happened. According to director Rob Cohen, it was because Weisz refused to portray someone with a 21-year-old son. Weisz simply did not like the script enough to sign on. Rumours circulated that Weisz chose not to be seperated from her (toddler) son at the time, but she has since made it clear that this had no impact on her decision whatsoever, and pointed to two other films that she starred in that very year.
In the closing scene, a screen text reveals that mummies were soon thereafter discovered in Peru, a possible stinger for a sequel (Peru is home to the ancient Inca civilization, which also mummified their important members). There was indeed going to be a third sequel titled "The Mummy 4: Rise of the Aztecs", but since Aztecs are native to Mexico, it probably would not have been set in Peru. Brendan Fraser and the cast of the third film had signed up for the sequel, and Antonio Banderas would have played the main antagonist. However, the film was canceled in favor of the reboot The Mummy (2017), which was meant to be the first chapter in the 'Dark Universe', interconnected movies featuring the classic movie monsters such as the Mummy, Dracula, Jeckyl and Hyde, the Wolfman, the Creature from the Black Lagoon and Frankenstein. However, due to the critical and commercial failure of The Mummy (2017), all other proposed movies were eventually scrapped.