With the help of DHTML we can show you two different strategies animators use.
To cut corners
some animators will reuse a single cel and just change it's placement on various
different backgrounds in order to simulate movement. Or in some cases create
a series of cels and reuse them in a cycle. [Like to simulate walking.] In a
similar way a background artist can create one long background, and then only
the different cels have to be redone and their placement can be moved on the
background and a new background doesn't have to be made. [If you've ever seen
animated chase in a hallway you've probably seen this technique used.] Below
you can make the ball roll throughout the hallway and see how the technique can
Below is an animated image that shows how the long background can be used repeatedly.