"Imhotep" was actually the name of the architect who developed the first pyramids in ancient Egypt, most notably the Pyramid of Djoser at Saqqara around 2600 BC. His ability was such that he was later said to have descended from the gods. His name means "one who comes in peace"
Ardath Bey, an anagram of Death By Ra, is the name of a sworn protector of mankind from the mummy Imhotep. However, in The Mummy, Ardath Bey is the alter-ego of the mummy Imhotep (played by Boris Karloff) when he attempts to pass for a modern Egyptian.
The opening voice-over was originally intended to be read by Imhotep. Director Stephen Sommers later realized that Imhotep wouldn't be able to speak English, and gave the voice-over to Ardath Bey instead.
When King Tutankhamen's tomb was found on November 4, 1922, the person in charge was George Herbert, 5th Earl of Carnarvon. Along with him was his daughter, Lady Evelyn Carnarvon. Rachel Weisz's character is named Evelyn Carnahan. Originally, her character was meant to be Evelyn Carnarvon. She and her brother were to be the children of the "cursed" Lord Carnarvon. The only evidence of this left in the film is in the line where Evelyn tells O'Connell that her father was a "very, very famous explorer". The Mummy novelization goes into a bit more detail on her back story.
A different take of Ardath Bey's introduction scene on top of the mountain was used later in the film when O'Connell and crew are crossing the desert at night. This time, the lighting was adjusted accordingly.
The locusts shown in the scene at Hamunaptra were mostly computer-generated, but a number of live grasshoppers were used for the shot; the grasshoppers were chilled in a refrigerator to make them more sluggish and easy to film.
In the scene on the riverboat, Beni is thrown overboard and into the river by O'Connell; during filming, Kevin J. O'Connor helped Brendan Fraser to appear as though he was throwing him overboard by jumping up.
In one scene, Beni is shown with a sackful of gold which he is trying to load onto a camel, and Beni pulls the camel by the reins but the camel doesn't budge; the camels all, for some reason, hated Kevin J. O'Connor.
The plastic dummies used as dessicated corpses in the film to represent the Mummy's victims are the same as those used in the cult 1980s sci-fi film Lifeforce. One character even refers to the Mummy sucking the 'lifeforce' out of people.
When Clive Barker was attached to the project, The film was intended to be a low budget horror film. Barker's vision for the film was violent, with the story revolving around the head of a contemporary art museum who turns out to be a cultist trying to reanimate mummies. George A. Romero was brought in with a vision of a zombie-style horror movie similar to Night of the Living Dead, but this was considered too scary.
Leonardo DiCaprio was rumoured to have been offered the role of Rick O'Connell, it's believed DiCaprio was said to have loved the script and wanted to be in it. However he already agreed to star in The Beach, it also said that DiCaprio asked if The Beach could be delayed so he could film The Mummy, but producers refused. However, filming of The Beach was delayed anyway.
The trivia items below may give away important plot points.
The lever-triggered slowly settling stone megaliths with sand pouring out like water, from which the characters must escape or be entombed alive, are based upon Howard Hawks' Land of the Pharaohs, where Pharaoh Cheops's tomb is constructed to be sealed in this manner after he is placed within. Historically no such sophisticated engineering technology was ever employed.
The location shown in the scene where Imhotep and his minions corner the protagonists was an actual entrance to a thirteenth-century graveyard in Marrakesh. In the shots of the graveyard entrance, a manhole cover was used for the surviving protagonists to escape; the manhole was constructed for the film and had a large pad inside so that the actors would land on the pad and not hurt themselves.