Update: Thanks for all of those who gave this a good rating. (And screw you bloody wankers who didn't :D). Feel free to contact me about it if you are an Actionscript 3.0 developer. Don't worry, I'll remove the second stages contents for you, and center the preloader :D.
Alright, so I spent months a while back trying to pull this off. I waited for someone to make one instead, because it was so unknown how to pull it off. I decided to try and tackle it again, and someone properly documented how to pull it off, so here it is: A newgrounds preloader for Actionscript 3!
Please don't judge it if your not a flash developer, seeing as you wouldn't appreciate this as much :D
This version uses an embedded MP3 and a visualization to prove it's use of AS3.
If the visualization doesn't work for you, I give up xD.
I tried fixing the security sandbox nonsense, and it's rough.
The song is In Flames - Sattelites and Astronauts.