Well, he doesn't exactly have any details you missed at low resolution, but here he is!
Early, scrapped concepts had a human doctor who was unambiguously villainous, even pushing his own alternative therapy methods for profit and now trapped in the hospital by mistake, but I didn't like that idea; it felt too obvious. The bad dude was scrapped and replaced with an entirely different human doctor, whom the readers by now have realized is not necessarily evil, but may not be all that he seems, either.
His design is taken heavily from the Laughing Salesman, a supernatural anime character who swindles humans in bizarre ways, as kind of a callback to the character Dr. Man wound up replacing. He would have a similar voice to the Laughing Salesman if you want to look him up on youtube.
My favorite joke with this guy was when I gave him a coffee mug full of green sludge and the commenters kept speculating it was some kind of poison, mucus, something no human would ever drink but all along it was a kale smoothie, something that only TASTES like inedible monster sludge.