When Ridley Scott set about making Philip K. Dick's novel Do Androids Dream of Electric Sheep? into a film, he knew there'd be some changes that had to be made to properly adapt it to the silver screen. One of the main alterations had to do with the "androids" in the novel, which Scott feared would be too similar to the Ash character he'd created for Alien. His daughter, studying biology at the time suggested something to do with "replication" and thus the term "Replicants" was born.
When Blade Runner was released, it changed the state of the science fiction genre with its ideas on artificial intelligence, futurism, and empathy. And while several aspects where altered from the concepts of the novel, as the "blade runner" Deckard hunted the rogue Replicants, he discovered what it meant to truly be human in both. Philip K. Dick died shortly before the film was released, but K.W. Jeter wrote several sequels to both the novel and the film. Below you'll find 10 facts about Replicants from the books the movies leave out.
REPLICANTS BEGAN AS MISTREATED SLAVES
The theatrical version of Blade Runner included much more exposition in the preamble, as well as a voice-over narration provided by Harrison Ford as Rick Deckard to make sure the plot wasn't too convoluted for viewers to follow. Much of that was lost in the Director's Cut, so was the extent to which Replicants were mistreated.
One of the main reasons that Roy Batty, Pris, and the other four Replicants escaped the Martian colonies were because they were slaves. They were made as slaves to serve humans, and mistreated egregiously as "skin jobs". Their abuse was largely dropped from the film for making them too sympathetic.
REPLICANT AGING CAN BE SLOWED
Though it isn't shown in the films, replicant aging can be slowed if the subject is placed into stasis before they begin to shut down, like the Roy Batty unit. This comes up in Blade Runner 2: The Edge of Human, when Rachael is placed into a Tyrell Corp transport container by Deckard after they leave the city at the end of the Blade Runner.
In the book, Deckard lives in a shack outside the city with Rachael, who had to be put into the container to slow her aging process. As long as she's kept inside, she's frozen in time exactly as she was, until Deckard can find a way to permanently keep her from aging. Her ability to reproduce isn't mentioned as a part of her model until Blade Runner 2049, and is taken from Blade Runner 3: Replicant Night.
REPLICANTS HAVE HUMAN TEMPLATES
When the Replicants are introduced in Blade Runner, audiences aren't informed about the creative process behind their conception, or why they were created to look the way they do. In the book Blade Runner 2: The Edge of Human, Deckard meets Sarah, Eldon Tyrell's niece and the template used for Rachael, when she tasks him with finding the "missing" sixth replicant.
He also meets the template for Roy Batty, who also desires to find the sixth Replicant. He believe sit to be Deckard. The Batty template has the same superior physical stamina and ruthless intelligence as his Replicant, which begs the question - is he just another improved model?
REPLICANTS WEREN'T ONLY MANUFACTURED BY TYRELL
While Eldon Tyrell is said to be the genius behind the Replicant, other corporations initially created similar synthetic beings, Tyrell Corp simply had a monopoly on the market. Th origins of Tyrell isn't explored in Blade Runner, Blade Runner 2049, or any of the books until Blade Runner 4: Eye and Talon.
A female blade runner named Iris is given an explanation that the UN destroyed the other manufacturers of replicants in order to create the Tyrell Corp artificially. Eldon Tyrell had simply discovered a way to manufacture them the best, and even help them house the gestalt of a human's consciousness, allowing them to transfer their mind into a new "body" every four years.
BACKUPS OF REPLICANT PERSONALITIES COULD BE STORED
In Blade Runner 2: The Edge of Human and its supplicant sequel novels, it's revealed that a Replicants' personality could be stored in the event that the host unit was destroyed. Rick Deckard kept Roy Batty's personality tucked away in his briefcase.
In Blade Runner 4: Eye and Talon, it's revealed that Eldon Tyrell's personality was stored inside the mysterious replicant owl that always fluttered around Tyrell Corp in Blade Runner. Taking the owl and a suitable replicant host body, Eldon Tyrell could be "brought back to life".
REPLICANTS COULD BE USED TO MAKE HUMANS IMMORTAL
In the fourth novel, Blade Runner 4: Eye and Talon, in which a female blade runner Iris searches for the Replicant owl that observed so much in the glory days of Tyrell Corp, readers are introduced to the concept of Replicants as a means to ensure immortality.
Iris finds several Eldon Tyrell Replicants, each with no eyes. This is to reflect when Roy Batty gouged out the eyes of the real Eldon Tyrell. They're waiting for Tyrell's personality (stored in the owl) to be merged, allowing Tyrell to live forever via Replicants.
REPLICANTS WERE GIVEN TO HUMANS WHO MOVED OFF-WORLD
Something that may not come across in Blade Runner is that humans are encouraged to go Off World by the UN in order to preserve the "genetic integrity" of humans. To entice them to move away from Earth, humans are given Replicants to assist them in their new life on an Off World colony.
These Replicants are called "andys" (short for android) are created by The Rosen Association on Mars, and are released to their human owners when they arrive. The Replicants aren't permitted to return to Earth, but assist their humans until their life span runs out (4 years).
NEXUS-7 LIFE SPANS ARE OPEN-ENDED
When Deckard meets Rachael and administers the Voight-Kampff questionnaire, with 20-30 questions designed to determine whether or not she's a Replicant, she exceeds 100 questions before he determines that she is. She's been implanted with human memories to make her the most human-like Replicant in existence.
Unless you saw the theatrical version, which included a voice over, you won't have known that Rachael (and all Nexus-7's) have an open-ended life span. This was removed from the Director's Cut to be left open ended, and in the sequel novel, Deckard is forced to put her in a Tyrell transport container to stop her aging process. In Blade Runner 2049, Nexus-9 Replicants' life spans are also open ended.
REPLICANTS ARE ROBOTS
Though the preamble in Blade Runner explained that Replicants were created as the culmination of advanced robotics and genetic engineering, they can't be compared to the androids in Ridley Scott's Alien franchise. Ash and Bishop were full of tubing, wiring, and microchip processors, whereas Scott wanted Roy Batty and Pris to be full of organic tissue.
In essence, they needed to appear "grown" in a lab, not fabricated in a machine shop. Scott wanted it visually conveyed that they could appear more trustworthy to humans by being similar to them. When they're injured, they bleed, and the only reason they were given empathy inhibitors was to prevent them from overriding the Voight-Kampff test. In Philip K. Dick's novel, they're described in much more robotic terms.
RETIRING REPLICANTS EARNS BIG BUCKS
In the novel Do Androids Dream of Electric Sheep? Deckard is more a bounty hunter, less a detective. He agrees to "retire andys" because it'll make him enough money to buy a larger real animal. Since radiation killed most life on Earth, organic animals (as opposed to those that are Replicants) are highly prized for their status.
Deckard lacks any empathy for the Replicants as a contract killer, which is appropriate for his level of hypocrisy, since he rarely shows emotion for his wife or fellow humans. At some point, as in the film Blade Runner, Deckard has to find a point of change, and learn to become more human by hunting those made in that image.