Of course Hobbes is real. Calvin and Hobbes is not the story of one kid’s tragic psychoses that lead to him beating himself up, e.g., to maintain his delusions. It’s a story about the thin dividing line between reality and imagination. In Hobbes case the line is crossed.
Hobbes is like hobbits–he is evidence that not everything from beyond the fields we know has to be eerie or eldritch. It is in this sense, and probably only in this sense, that Calvin and Hobbes could be considered a Mormon comic.