The original idea for the first film was too ambitious. You see, originally Skynet was going to send two machines to kill Sarah Connor, the first being the T-800 we know and love. The second… Well, stop me if you’ve heard this one before, but the second was going to be a shape-shifter made out of liquid metal.

Yes, the T-1000 was in the original concept, but the effects of the time weren’t good enough to make on a mid-to-low budget, so the character was scrapped (and eventually revived when digital effects made the T-1000 possible).