Trivia: Originally intended to be a 30-minute short as part of an anthology film, though it became so ambitious it was made into a feature-length film.
Trivia: An unused alternate ending for the film would have Susan and Chuy escape into a subway platform, where they'd be greeted by dozens of men in long coats, with it being left vague whether or not they were humans or "mimics" of humans. This ending was reportedly even shot and shown at a few test-screenings, where it proved to be unpopular, and thus was replaced by the more "happy" ending in the theatrical and director's cut releases.
Trivia: In the original ending as intended, the "King" of the Judas Breed wouldn't be killed by the train, but would rather in silhouette form back into a human "mimic." He'd step out of the shadows to reveal the perfect image of a nude human male. He would then point at Susan and in English tell her to "leave", implying that the Judas Breed had reached such a stage in their evolution to be able to perfectly mimic human beings, even down to speech patterns. This was in keeping with the original, much more apocalyptic tone of the story before script-changes forced by the producers.
Susan Tyler: When I increased the Judas' metabolism, I must have sped up its breeding cycle. I mean, we're talking tens, hundreds of thousands of generations, who knows how many mutations.
Peter Mann: I don't get it, I just don't fucking get this. How could the Judas evolve into this?
Susan Tyler: Think generations, not years, okay. It took only 40,000 generations for apes to turn into humans.
Peter Mann: So?
Susan Tyler: We changed its DNA, Peter! I mean, we don't know what we did.