I was thinknig that what if Liu Kang was the sub-boss? That would make sense because he'd be a playable character. Then using the common knowledge that Liu can turn into a dragon, what if he morphs into Onaga, the Dragon King himself? That would definitely be a big twist and would explain why Liu unexpectedly returned to the living world. Since not many of the endings happened in Deadly Alliance, it's possible that Reptile isn't the Dragon King and Liu may be. Either that or I'm crazy.