Pops" is a T-888 Terminator and Model 1000 Infiltrator sent from an ... for him to be unable to smile normally as liquid metal can perfectly mimic.It's established early in the film that the poly-alloy can be used to repair the terminator. When the T888 finds the "killed" young Arnie T888 you'll notice it drops some of itself into the head wound. This brings the T888 back to functioning again to chase Kyle Reese.You may recall that he explains this; he didn't die, he was 'upgraded'. They never really specify what that means, but I believe it has to do with him being coated with the liquid metal.