My "earring theory" is probably best suited for the Halloween season. BUT! I couldn't help but think to a scene from the movie "Ginger Snaps." One of the characters gets bit by a werewolf, and in order to suppress or slow down the change, said character's sister suggests a piercing made of silver. Now consider that Kakashi goes on a lot of solo missions, and has faced down both man and beast. Sakura is very perceptive when it comes to Kakashi; she'd know that something was amiss . . .
DID YOU JUST.
DID YOU JUST MAKE KAKASHI A WEREWOLF, OHMYGOD.












