Rig them to do what?

You could rig them by first projecting them onto a polygon plane that matches their outlines then binding a skeleton to each but they would still just be 2D images, like an animated piece of flexible/elastic paper.

I think that if you made 3D models, you could apply a cartoon shader to make them look 2D. By doing that, you could have them move as though you drew them from any angle and animated them like traditional cel animation.