Okay, so we've all read about the mysterious Koffin WQ, and it got me thinking: what if it was related to the Kombat Kodex in the Brady Games Guide? So, I found a copy of the Kodex and had a look, and lo and behold, W and Q have fighters below them! W is Sub Zero and Q is Nightwolf!
Here's where my theory comes in: What if a secret is unlocked if you move from Sub Zero (W) to Nightwolf (Q) on the character select screen (by moving the control stick diagonally bottom-left), then press left (4 on the Kodex), Attack Button 3 (5 on the Kodex) and Up (6 on the Kodex) simultaneously? Or maybe press the buttons in order? Hopefully someone will try this to see whether anything happens.
I also came up with another theory. As you may know, some characters in Konquest talk backwards. Well, someone decoded this, and one of the things said was "Ed Boon: 490". This got me thinking. I think this sentence is possibly a code. Maybe you should go to the Krypt and open these coffins in order: ED, BO and ON. If nothing happens, maybe you should then press Left (4 on the Kodex), Block (9 on the Kodex) and either Start or Change Stance (0 on the Kodex). Hopefully this could lead to something...
I'm not making this up: I'm saying this will work, but I'm just trying to help you in your quest for more unlockables. This could be the key, or it could just be total rubbish, but hell, surely it's worth a try?