Why did Holden need to VK Leon, if the police knew what he looked like? This test is more crucial in the novel, where it is intimated that there are humans who have actually been replaced by look-alike replicants. Replicants, however, can readily change their appearances and aren't easily recognized from photographs, e.g., Zhora's tattoo, and Pris' raccoon makeup. In the July 1980 screenplay, Deckard muses, "They could change their appearances but not their future." In the December 1980 screenplay, Deckard says Zhora's "black hair is a wig which now hangs on the wall next to the shower. She didn't look like Nexus designated Zhora to begin with, but even less now."
Bryant tells Deckard that there were six replicants, three male, three female. Obviously, Roy and Leon are two of the males, and Pris and Zhora are two of the females. Bryant also says that "one of them got fried trying to get into the Tyrell building", but doesn't specify the sex. That leaves one replicant, either male or female. It has been hypothesized that Deckard was the sixth replicant, but there is ample evidence that this is not the case. In an earlier version of the script "Mary" was the fifth replicant, and "Hodge" was the sixth. Bryant's line in that script got past the screenwriter unnoticed. It was recorded correctly in the Workprint as "two got fried" but botched again on the release print.
Why is it so difficult to tell a replicant from a human, when replicants can put their hands in boiling/freezing liquids without damage? Surely a tissue sample would suffice? Perhaps, but Holden couldn't even get a straight answer from Leon, much less a tissue sample.
How did word of Rachael's escape get out so quickly, and how could Tyrell tell that she had gone for good? Remember that Deckard called Rachael at home while he was still at the nightclub. It could not have been more than a couple hours before he gave chase to Zhora. (How long could she "take the pleasures from the serpent"?) Was that enough time for Rachael to run away then for Tyrell to call the police and have Bryant put Deckard onto her? Another explanation is that Tyrell's "experiment" was voided when Rachael discovered she was a replicant; Tyrell simply used this opportunity to dispose of her.
How did Roy get into Tyrell's office so easily? Did Tyrell trust Sebastian enough to give him the option of bringing anyone/anything up in the lift? Tyrell was unaware there was anyone in the lift with Sebastian until he said "I brought a friend." In earlier scripts, Sebastian and Chew both held the highest security clearance.
In an early version of the script, Tyrell was a replicant, and Roy picks up on this because of a key both Sebastian and Tyrell are wearing. In that version, the real Tyrell was in a "cryocrypt", sketches of which appear in The Blade Runner Sketchbook. After Roy kills the replicant Tyrell, he makes Sebastian show him the crypt where the real Tyrell lies dead because of a mistake Sebastian had made.
