I don't know exactly if it's just an animatic (a very good one, by the way) or a promo short for the release of Up in DVD and Blu-Ray. One thing I know, though: it's another hilarious Pixar short! :)

It seems like this is an animatic made to pitch an idea to be included as an extra of the DVD/Blu Ray. Since the short produced for the disc is "Dug's Special Mission", I believe this could be a rejected idea. But it's was so cool to be called "rejected" they decided to release it online.

And in case you didn't see, Blender 2.50 Alpha 0 is available for download. This is the first of five alpha releases before it's considered stable and finished. I've been playing with daily self compiled builds from SVN and I can say it is getting sexier each day. :)