Space Jam

So I was listening to the Space Jam soundtrack yesterday and began to wonder how they shot the movie. The cartoons play such a big role in the film, it must have been difficult for the actors to play their parts with no one there. I also began to think, how exactly would you be able to get the looney toons to look active and natural within a scene. The concept intrigued me, I'm not sure how you would go about doing that. The movie came out in '96 so they couldn't have used anything very high tech.