He's arachnaphobic because a bully once stuck the science teachers large pet spider in his locker and it jumped on him, the bully got a looonngg detention for it
He has some severe trauma in his past that he does get the occasional nightmare about, but he started getting better after so many years
He once hit his head so hard he needed stitches, he got sensitive over it so his sister gave him a purple beanie and he always wore one since then
He grew his hair out to be more like his sister