What is the technique call in cartoons where they use the same background over again?
You know, like in those old hanna-barbara cartoons like the Flintstones and Huckleberry Hound. When the characters are running, driving, etc, they pass by the same objects in the background. And I am aware that this technique is still being used today.

it’s called a repeat pan
http://www.youtube.com/watch?v=i_D6Yt6KCmI
they used to have a music video for this song with clips from hanna barbara cartoons and they used to play it on cartoon network
That’s called "cheating".
I’m not sure of any technical lingo, but in everyday use that’s called "recycling animation."