Max Hass.
Hodor, HODOR!
Lol totally thought of the same thing when I saw him. However, whatever whammied this guy, hit him pretty hard given the shape of his head. Unless its a birth defect. Still, he is awfully adorable. Hope he survives. (Currently in the beginning of Chapter 10.)
Knowing what we know about historical Nazi medicine, it seems probable that he had some kind of interesting disease--perhaps some kind of glandular cancer which could also account for his physical qualities--and was subjected to treatment designed solely to be amusing to the physician.
And presumably was released to die, or escaped.