visually its pretty much perfect
first off, wow, those backgrounds were fucking beautiful, especially the christmas lights that came to life; it's not often you get flash animations that have so much detail put into the lighting aspect
i've got to nitpick a few things though. i don't think the flash should have turned out to be the kid's fantasy/dream. something that's annoyed me recently about a lot of cartoons is that the cartoonish and fantastic aspects of them turn out to be a hallucination, a dream, or a drug trip. it's not only an easy 'cop out' ending, but it sort of takes away from the fact that it's a cartoon in the first place. personally i think the story would have been stronger if you based it around the city with the boy encountering the neon lights, rather than taking it to the outer space setting. a few things seemed shoe-horned in as well, like the alien for example - i think he was just there so the cartoon could have a tangible antagonist.
aside from that, everything else was great (especially the shots/framing), the sequences fit well with the music etc etc etc, i just wish more of the cartoon was like the first minute or so instead of a space adventure