So, this will be a short theory and probably wouldn't be accepted by others:

I believe that Mike is Knight, because some believe that Mike controls Kris, and Kris creates a fountain at his house during the ending cutscene. Maybe, Mike is Knight? I might be wrong because Queen said anybody can create a fountain with their DETERMINATION, and Mike is controlling Kris to use his DETERMINATION and create a fountain with it (and Berdly almost created another fountain with his Helberd). This is my theory, and won't be likely true.

Anyways, I will not force you to accept it.