He believes they're real himself. Like, he's aware that some "naive" people exist in the world who don't believe in alternative dimensions, but Chris would just talk down to such people. "ugh, you're so close minded, it's obvious that magic is real"
Now what would be interesting is if they drew their character (doing it competently, of course, in comparison to Chris' chicken scratch) telling Chris that they've never met him in the other dimension and that he's harassing them over there and they're going to call the cops if he doesn't fuck off.
I don't think he really has been.
He's usually flattered when people draw his characters. (After he nitpicks all the autistic little details they got wrong, like the color of Sonichu's shoes or whatever.)