How Many POVs Do You Have?

What do you do if some of your characters don't like exist it's such a fun question because I can think of so many different reasons that you might have for this. The first thing that pops to my mind is Calvin and Hobbes and how Hobbes is real for Calvin but not for anybody else. Part of the question is how many POVs do you have if you have more than one POV and you can have that other POV revealing that a character is not no one else is noticed.