Terminator 2: Judgement Day - Head in the Back Window
After Arnold steals the police car, he drives it backwards at high speeds. If you look closely though, you can see a person and a steering wheel in the back seat of the car facing toward the rear. Someone is right there driving the car.
In T2, "Special Edition", available on DVD, the filmakers discuss how the car was driven backwards by a stunt driver "hidden" in the back seat. So it wasn't a slip-up, except for the fact that the stunt driver wasn't too well hidden from the more alert movie-goers. Congratulations, "Eagle-Eye".
Hey, that's definately a slip up!!! Yeah, they might say that's how it's driven in the Special Ed, but the driver is not a character in the movie... Your concept of slip-ups is bizarre....