Freddie Boath passed on the opportunity to play in Harry Potter and the Sorcerer's Stone (2001) to participate in this movie, because The Mummy (1999) is one of his favorite films. He knows so much about the movie that he even served as sort of a consultant on the first film for the other crew and cast members.
London's Tower Bridge was closed to allow for filming. They were allowed to close it for 20 minutes at a time, but the resulting traffic jam after the first time brought threats of arrest from Scotland Yard and a reduced closing time of 10 minutes.
Although the characters of Rick and Evelyn had grown and matured in the second film, Director Stephen Sommers wanted it to be clear that Jonathan had learned absolutely nothing from his first adventure.
The title does not appear at the beginning of this film. The title finally is given at the end of the picture, after the headlining credits but before main credits roll. Now common, in 2001 leaving the title off the start of a film was a relatively rare innovation.
When Alex stops the train in order to escape, Imhotep steps out of the wagon together with Ank-Su-Namun and gestures that they have arrived at the destination, calling it "Karnak". However, Karnak is a modern name of the temple meaning "fortress" in Arabic. The ancient Egyptian name for Karnak was "Per Amen", meaning "House of Amun".
Ardeth Bay (Oded Fehr) is the only person in the film who refers to Imhotep (Arnold Vosloo) as "the Creature"; this is explained in the novelization of the film, which states that Ardeth fears, as do all Medjai, even referring to Imhotep by name while the mummy is still in his undead form, calling him "He That Shall Not Be Named". Ardeth Bay in the novel overcomes this unease and reluctantly refers to Imhotep by name after the mummy's regeneration.
When the O'Connells run out of the museum after Rick rescues Evie, there are four mummy guards chasing them. However, in the ensuing bus battle scene, only three are killed. According to the original script, the fourth was supposed to attack Alex after the bus had come to a stop. However, director Stephen Sommers decided to cut the scene, figuring that the audience had had enough of the mummy battle and wanted to get on with the story.
In Evey's first vision, which shows the bracelet being locked up, it is evident that she sees herself but as Nefertiri. She is wearing the same clothes and ornaments, the night Pharoah is killed by Imhotep and Anck-Su-Namun.
The building used for the outside of the British Museum is not the real British Museum; it's University College London. The Museum was unavailable as it was undergoing external reconstruction and was covered in scaffolding.
The trivia items below may give away important plot points.
When Evelyn is first seen brushing off a wall, the figures on the wall behind her are of two females fighting with sais. This is a depiction of her as Nefertiri fighting Anck Su Namun in front of the Pharaoh.
The scene in which the Curator's hand was torn off is explained in the novel of the film: the pygmy mummies used the pyramid of Ahm Shere as a place of worship and savaged intruders in any way they could, and in that version, the Curator's hand was not stripped of its flesh but completely torn off instead.
The events behind the Curator Baltus Hafez's demise appeared in a somewhat different manner in the film's novelization: Hafez's name was "Faud Fachry", and he wore an off-white suit with a simple fez instead of his more elaborate clothing shown in the film. Along with this, Fachry mutilated himself when in Ahm Shere: in the book it was revealed that the Scorpion King's people followed an ancient ritual that required someone seeking total trust from his master to scalp himself: the Curator does this, as does Imhotep before the Scorpion King. Imhotep proclaims the phrase "Mi Phat Ahs", meaning "I am your disciple" to the Scorpion King and is spared; the Curator, before he can show his scalped skull, is stopped by O'Connell, who, while escaping the Scorpion King takes the golden helmet from a statue and rams it on the Curator's head, mispronouncing the phrase as "*your* fat ass": O'Connell's doing this was explained as putting the Curator out of his misery. The Scorpion King does not see Fachry's gesture of submissiveness and kills the Curator at once.