San's original form bursts free of the drug needles used to keep his fake form going, and looks more like that of a pale goblin. His thumbs were swollen since birth, and is not the hyper, whiney, crybaby San he was but rather his true self is being brain damaged (which is permanent), more accidents happening, can blimp very easily (both figuratively and literally), a butt that has growing puss (expands his buttocks rapidly to the point that it can fill an entire room if the puss is not out), has cerebral palsy and severe autism but can at least crawl (though he crawls more like a baby), and has no seizures but does have developmental problems (meaning he functions more like a toddler/baby). The puss did did get removed completely thanks to Cat, but the painful transformation of containing his true form and self caused him to have traumatic brain injury (permanently). Nevertheless, he's currently doing well at his nursery bedroom that the commander of the guild planned for him.