I'm almost sure this is an old Twilight Zone or Outer Limits episode. I don't remember much: A man discovers there are robot/android/thingamajigs living secretly amongst us. Oh, my! Of course, once he finds this out, the bad guys are after him. At the end of the episode he is being chased and runs across a street and a car hits his arm. When he looks at his damaaged arm, under the skin there are wires and mechanics. He realizes he's one of the robot/android/thingamajigs! Oh my!