To kill or not to kill.
Arnold originally met with the team behind The Terminator about the role of Kyle Reese. Arnold was looking for heroic leading man roles, not villainous killing machines, but James Cameron coaxed him into playing the T-800 by assuring him that The Terminator would be such a cool character, audiences would root for him. In a fun twist of fate, by the time the sequel rolled around, Arnold had the opposite concern: he was afraid that audiences might reject a Terminator who doesn't kill. This is where the idea that John Connor had to order him not to kill originated.
T2 used ideas that had been scrapped from the original.
The first Terminator movie was at one point going to feature an evil Terminator and a good Terminator duking it out, both of them played by Arnold Schwarzenegger. However, the original movie's budget didn't allow for the kind of special effects trickery that would have been necessary to convincingly pull that off. There also wasn't enough to realize another of Cameron's earlier concepts: the idea of liquid metal.
Billy Idol was the first choice for the T-1000.
In a 2017 interview with The Hollywood Reporter, Robert Patrick revealed that he actually saw rock star Billy Idol's image when he first went to Stan Winston's studio. Apparently, Billy Idol was all set to play the new Terminator, but was sidelined by a 1990 motorcycle accident, which messed up his leg. In Billy's 1990 video for "L.A. Woman," the punk legend that once fronted Generation X walks with a cane. "L.A. Woman" is a cover of the classic song by The Doors. The injury didn't prevent Idol from playing Jim Morrison's injured drinking buddy, Cat, in The Doors movie.
'Hey man, nice shot.'
Speaking of rock n' roll, Patrick also told the The Hollywood Reporter that his agent sold him to the production as Idol's replacement by describing him as a mix of James Dean and David Bowie. He made sure to have an intense presence for the casting director, giving her that now well known T-1000 stare. Robert Patrick, who went on to star in later episodes of The X-Files, is the older brother of Richard Patrick, frontman for Filter, whose hits include "Take a Picture" and "Hey Man, Nice Shot."
The lengths the T2 team went to come up with sound effects for Arnold's liquid metal adversary were experimental even by hard rock standards. The sound of the T-1000 transforming, for example, was a recording of dog food coming out of a can. Another sound effect was reportedly achieved by wrapping a microphone in a latex condom and then sinking it into a mixture of water and flour brought to a boil.