Actually, no. I don't watch Buffy, actually.

I have another friend (who I've known longer) with the same name as him, so before we began dating my sister dubbed him the Other Z, or OZ for short (it just got confusing otherwise). The nickname just kinda...stuck. I actually call him that more in real life than his true name.

His old college friends who knew him by a different nickname or his real name actually like Oz a heck of a lot better, and it's approved by him, so it works.