I actually found this looking for the music from Harry Potter and the Methods of Rationality, only to find the guy that made Castle used it in a 2005 animation? Wow!
The cinematography and timing of the audio is really fantastic here. The art and animation are serviceable but look almost more like an animatic than a finished product. Then again, for over 3 minutes of animation it would have taken forever for something like this to be as fleshed out as a more polished product, and that's not taking into account that even the very best Flash animations in 2005 didn't look much better than this. A few sequences feel drawn out when it's obvious you were trying to get later sections to sync with the music but overall this looks great.