Apart from some sterling writing and production values, one of the interesting things the piece tries to do is bring the hand drawing feel to their CG renderings by actually overlaying them onto keyframes with the computer doing the rest. This idea certainly gives the piece a different feel and doubtless there is more that can be done in this space to broaden the visual pallet of CG animations. These two behind the scenes videos give us a glimpse of the work and the R&D needed to bring this little film to us - wonderful stuff.
To finish up, here are a few images from Paperman showing the final look as well as some of those wonderful concept and pre-production sketches (see Paperman site for more). Disney has a great talent pool and it is nice to see that translating into side projects like this one!
[Paperman images via ]