I have a theory about Ghoul Balloon Boy:

I surmise that Ghoul Balloon Boy is a representation of Mike's childhood shadow, corresponding to the Ghoul Balloon Boy's introduction in the Old.lore(he is a symbol of broken hearts). Mike may have had some tragic experiences in his childhood, such as the death of Mike's parents due to an accident, which made him not have a happy childhood, even in his adult life, he still can not forget that experience, which led to the birth of Ghoul balloon boy.