The character Molly Millions, from the original story, was changed to Jane for the film. They are very similar characters except that Molly had retractable razor blades under her fingernails and augmented vision. It is believed that the change was due to the "Molly" character being attached to the rights for any possible future Neuromancer film adaptation.
During the scene in the back room of Crazy Bob's Computer Store it sounds like Johnny asks for an "iPhone", 12 years before it was launched - while it would still be cute if the script writer of a 90's cyberpunk movie had just made up a word which would later become the name of a ubiquitous piece of information technology, what Johnny asks for is actually an "Eyephone", an early head-mounted interface designed by Jaron Lanier (in fact, Johnny calls it a "Thomson Eyephone", a reference to the fact that Lanier's patent was bought by Thomson Electronics).
The film was shot on location in Canada, with Toronto and Montreal filling in for the film's Newark and Beijing settings. A number of local sites, including Toronto's Union Station and Montreal's skyline and Jacques Cartier Bridge, feature prominently.
Three music scores were created for the film. The first, composed by the band "Black Rain" at the request of director Robert Longo, was not used in the film and was subsequently released on a CD album. The second was composed by Mychael Danna and is still featured in the Japanese version of the film. The third score was composed by Brad Fiedel at the request of Sony and is featured in the internationally released version of the film.
Robert Longo and William Gibson originally envisaged making an art film on a small budget, but failed to get financing. Longo commented that the project "started out as an arty 1½-million-dollar movie, and it became a 30-million-dollar movie because we couldn't get a million and a half."
Sony realised early on the potential for the reaching their target demographic through Internet marketing, and its new-technology division promoted the film with an online scavenger hunt offering $20,000 in prizes. One executive was quoted as remarking "We see the Internet as turbo-charged word-of-mouth. Instead of one person telling another person something good is happening, it's one person telling millions!". The film's website facilitated further cross-promotion by selling Sony Signatures-issued Johnny Mnemonic merchandise such as a "hack your own brain" T-shirt and Pharmakom coffee cups. William Gibson was deployed to field questions about the videogame from fans online. The habitually reclusive novelist, who despite creating in cyberspace one of the core metaphors for the internet age had never personally been on the Internet, likened the experience to "taking a shower with a raincoat on" and "trying to do philosophy in Morse code."
William Gibson was very unhappy with what became of this adaptation of his own story. Despite being credited as the sole screenwriter, he has insisted for years that it wasn't his screenplay that was ultimately produced.
In this film, Keanu Reeves plays a man who smuggles data from cyberspace. Four years later, he starred as a computer hacker who learns that he has been living in a computer program in The Matrix (1999).
The unbounded spread of the Internet in the early 1990s and the consequent rapid growth of high technology culture had made cyberpunk increasingly relevant, and this was a primary motivation for Sony Pictures's decision to fund the project in the tens of millions.
In Doctor Who: Time Heist (2014), there is a character in that episode played by actor Jonathan Bailey called Psi. Like Johnny, Psi has the ability to store data in his mind and also like Johnny, Psi has deleted all his memories of his family.
Dina Meyer appears topless in the film, but only her bare back is seen. The actress wouldn't be seen fully nude on-screen until Poodle Springs (1998). However, in Starship Troopers (1997) only her bare breasts are seen.