Texture rip of Nightmare from Extras menu.
So, does he represents the kid's whole trauma from animatronics and the bite? The only parts that aren't transparent (which means they are the only important parts) on him are endoskeleton (which is main part of the animatronic), teeth and brain (which are exactly what was involved in the bite). Well, this and bowtie along with the hat. Anyway, this explains his name and lack of any normal name like Fredbear, Chica, Bonnie, Foxy and Freddy have.