Ghost mobs: Harmless yet just as scary.

Would anyone else be interested in the ghosts of mobs like creepers showing up? They'd look exactly like their non-ghost counterparts but be completely unable to harm you (or wouldn't drop wool or pork in the case of sheep and pigs). Imagine a creeper running at you and you have no idea if it's a real one or a ghost one.. but you run away anyway. It seems like the sort of evilness the game likes to show sometimes. What does anyone think of the idea?