The creature that hunts down the Doctor before being shot down by the Sniper girl is actually the original design of the Predator that was scrapped during Predator 1 due to issues with the costume and the jungle. The original Predator was supposed to be very slender with backwards knees and long arms, but because of the jungle setting, it was scrapped because the director was unable to make the costume work properly. See more...
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Continuity: When the group choose to leave Cuchillo behind and Isabelle decides to put him out of his misery, there's a fraction of a second where you can see his would-be-bullet-wound on his back explode from a supposed bullet impact without the gun being fired as Isabelle takes aim, only to go off again after Isabelle shoots him in the following shot.