If he's right about the characters coming from another game, then it's a fictional game that does not exist and isn't going to exist any time soon, because Dan said Project Libitina is unrelated to the next game. Also, some of the content MatPat is highlighting as being part of the theory is actually fan art that Team Salvato got permission to sell merchandise of, so any hidden meanings there are derived from fan theories themselves instead of being canon material placed there by the author.
@Ari, should I be concerned if I'm being
wathed?
And yes, we did bring up the pictures. I even went so far as to describe how I would have figured out that stuff if I hadn't had it spoiled for me.