Ever notice that funny metal bar underneath KITT's front nose? You know, the one that hangs down so low that KITT would have to turbo boost over a parking curb just to clear it.
Here's a closer look:
While this feature has become an official part of KITT's "look", it is actually a receiver for a camera car hookup. In the first two seasons, and the beginning of the third season, The receiver looked like you see it above. A camera car would connect two pins to either side of the receiver and then pull KITT while they filmed interior shots. This first generation setup was permanently welded to the car's unibody.
In the third season, the receiver was redesigned to be less noticeable. See below:
Notice how the huge metal bar is gone, replaced with two small receiver holes? These new receivers were simply bolted on the car. When it was time to tow the car, the camera operators would then connect the previously seen bar to the receiver holes on KITT, then connect that to the camera car, and tow it as usual.
Finally, here's a great shot from the set of "Knight of the Drones" where you can see the whole setup in action!