Boy it's been a long time since I've been here last! That's not important, though. What is important is that I decided to mess around with Dolphin a bit!
Let's start off small. Listed between N96CD_01.adx and N96CD_24.adx is the entire soundtrack to the original NiGHTS into Dreams! Almost none of it is used. Even jingles that are shared between both games already have a file in the main soundtrack listing. The unused songs include things like Stage themes, all the boss themes, Cutscene themes, and even Know Thyself!
I guess Selph is double unused now?
Behold, the Test level! There are actually 3 test levels in the game, but they all seem to be based on the same geometry. For reference, the one here is Test03.
To load this I extracted the contents of the ISO with a tool like QtWitGUI, switched the folder for the first mission of Pure Valley (Stage1000/Level00) with Test03/Level00, and then rebuilt the ISO.
When I first spawned, Will spawned underneath the floor into the endless void. That's bad, can't have that happening. Luckily, there are some conveniently placed LUA files in lua\stage\stage1000\ that control properties of the level! I set the spawn coordinates to 0,0,0, and the collision worked!
I don't know where the stage layout files are to see where things like chips, NiGHTS, and other objects are supposed to be, but the Arrangement folder shows that there's a simple track for NiGHTS to fly on.
Here are some other fun things from when I was messing around:
http://i.imgur.com/5rmmd6u.png - I don't know but I'm spooked.
http://i.imgur.com/adXaM7l.jpg - Reala?!
http://i.imgur.com/Y3yKIwZ.jpg - Double Reala
http://i.imgur.com/3BpLICu.jpg - Oh, you don't look so good....