Interesting Concept
I like the concept of using the same kind of animation that Valve used themselves in the advertisement of "Portal" and for the most part it worked. But it seemed to me that some of the animation (in terms of style) seemed inconsistent and dry.
For example the characters and rooms were sort of bland and rounded and seemed to fit together, but when you introduced the cake, GLaDOS and other things that weren't originally made by Valve, they just seemed to be too colourful/they just didn't seem to fit for me.
It is a very basic form of animation and it worked well for Valve because they used it in short videos with simple ideas. What you've tried to do is make that animation into a bit of a story which is very difficult to do.
This is all not to say I didn't like it, other than that it was somewhat entertaining, although I would have liked to see more movements/actions associated with the beat/timing of the music.