James Cameron's original plan was to include the liquid metal T-1000 as a second villain in Terminator 2's T-800 being the most iconic hero - the T-1000 definitely comes close. The shape-shifting cyborg remains actor Robert Patrick's most well-known role, and it probably always will be, even though it's the one that originally put him on the pop culture map.
The T-1000, like the T-800, is made all the creepier by the eerie calm it exudes, with Patrick's steely gaze enough to intimidate just about anyone. Also like the T-800, it can't be bargained with, can't be reasoned with, and absolutely will not stop until its target - in this case future resistance leader John Connor - is dead. The difference is, the T-1000 is a much more advanced Terminator model, and therefore much more capable of making said death happen.
The T-1000 is such a famous ingredient into what makes Terminator 2: Judgment Day one of the best sequels of all time that it's a bit crazy to imagine it simply having been an additional boss battle in the first film. Yet, for a time, that was the plan.
Terminator 1 Almost Included The T-1000 - Why It Didn't Happen
James Cameron's original story plan for The Terminator was much more ambitious than the final film ended up being, which despite some great sci-fi concepts, was essentially a slasher movie with a cyborg villain. Cameron originally planned for the human resistance to send back two protectors for Sarah Connor, instead of just Kyle Reese. The other man would've been killed fairly quickly though, leaving Reese to protect Sarah as fans have come to know. However, partway through the film, Reese and Sarah would manage to take out the first Terminator sent back by Skynet, leading the machines to send back another experimental model made of liquid metal to finish the job.
It's readily apparent that this idea was way too complex for the first film in a franchise, especially one made by a director who had yet to become a force in Hollywood, and thus couldn't command a huge budget to work with. Money worries, combined with Cameron's belief that the special effects techniques of 1984 couldn't successfully realize an amorphous villain like the T-1000 properly, led the writer/director to reduce The Terminator's script to one man vs. one machine in a battle to decide Sarah Connor's fate. After The Terminator was a hit, and special effects technology had improved, Cameron resurrected the T-1000 idea for Terminator 2.
