Jennifer Jason Leigh had already finished shooting her role in Eyes Wide Shut (1999) when she took on this role. When her scenes in that movie required re-shooting, the schedule required for it interfered with this one. Leigh chose to stay on this movie, and her role in Eyes Wide Shut (1999) was re-cast.
Two producers of this movie are Hungarians, so it is not by chance that the X and the Z of the word "eXistenZ" are capitalized, since the letters between them make the Hungarian word "isten", which means "god".
Jennifer Jason Leigh insisted on keeping one of the prop pods with her in between filming to strengthen the maternal bond you see in the film.
David Cronenberg claimed his inspiration for the film, was the fatwa declared on author Salman Rushdie, following the publication of his book "The Satanic Verses".