As you may have noticed, I've been using "Zombie", instead of "zombie" when describing Billy, and those like him. You've probably wondered why I capitalized the "Z" in "Zombie".
Billy is not your average movie/video game/RPG zombie. He's intelligent, peaceful (although he will fight if necessary), and has no intention of eating anyone's brains or flesh (which he would probably find very disgusting). I treat Zombies like Billy like a race (hence, the capital “Z”), meaning that there might me more of them.
When referring to Billy, or any Zombie like him, please use the capital "Z". Any other kind of zombie can be referenced as normal, with "zombie".