Something to download (e.g. through Video Downloader) and study more thoroughly. You'll need a FLV viewer, though (information provided on the Video Downloader website).
Wow, that's an amazing bit of animation. I'm assuming it was done in the traditional way, but I bet this could be done in AS. This really shows the importance of good drawing skills as a good base for computer animation.
Here's a link to a program called TubeSock, which, if you're a Mac user, downloads YouTube movies easily and with good quality:
I just read that Google has acquired YouTube. I wonder if that means they'll gradually make all the movies viewable in only the Google Player. If so then TubeSock may not work anymore for that in the future.
Well, I'm not the creator of that animation, I just saw it while watching YouTube.
@JCook: That would break a lot of websites, because many websites (weblogs) use YouTube videos for their content. Anyway, you can download Google videos with other tools as well (with the forementioned Video Download).
I read a little further about the Google-YouTube takeover, and it seems that the two will still run independently, so there may not be a problem after all with that. Things change fast in CyberWorld!