I am the curator of the #DNDOOC channel at rizon.net (no longer at suptg thanks to the diminutive tyrant known as PurpleXIV) and sometimes people stumble in not knowing that the channel's been taken over by grognards. Sometimes they do realize and don't care, figuring that anything with DnD in the name stands a fair chance of getting answered. The sad fact is, though I've played 3.x and 4e, I don't know them back to front so I can't really answer game-design questions when it comes to "how can I balance this?" or "does this make sense according to the rules?" While I can roughly estimate the amount of damage a level 5 warrior will do per-round in AD&D (1d8 assuming arming sword, with a THAC0 of 16 means at least a few hits, plus whatever magical bonus the weapon has) I really can't calculate the huge levels of hp damage dished out by Pathfinder or 3.x characters.
Which brings us to the problem: the sheep. One of the folks who's an on-and-off visitor to DnDOOC asked about translating a sheep from 3.x to Pathfinder. Apparently, this sheep was integral to the adventure. He had a stat-block in front of him for the sheep and was wondering the proper procedure to take a docile animal from 3.5 to the Paizo system.
I didn't understand.
What difference does it make, I asked him, what the stats of the sheep are? No one will ever meaningfully interact with them. If someone wants to slaughter the sheep, they'll just take a round and cut its throat.
This wasn't answer enough.
"Every living thing has hp," he said (in what I imagine was a terse manner), "and I need to know how much."
This baffled me. While there are stats for sheep in 2e (2 hit dice, 1-4 damage, 3 xp) I couldn't understand why he needed this number. I asked if they were going to fight the sheep and he said they might decide to slaughter them all. Well, slaughtering isn't really fighting—if so, every farmer would have to roll a d20 to see if his axe hits the chicken's neck and roll for damage to see if he successfully killed his cow. This seems ridiculous to me.
When would a sheep's hp come in handy? I suppose if the party was guarding some and they were attacked, but even then you could just make the decision that it takes x number of minutes to savage them fiercely.
I brought all of this up, and even pointed out that you wouldn't bother to roll damage against a sparrow if someone shot at it—you'd just see if the arrow hit and, if so, the bird would be dead (or mostly dead, DM fiat can come into play for effect). He corrected me. Sparrows have hp ratings and xp value, he said, so you must roll for damage when you strike one.
Well, now, there's a case where the AD&D MM doesn't have any stats and for good reason I think. What, after all, is the purpose of the hit point mechanic? It is to show the slow gradations of wounds leading up to the killer wound, the one which incapacitates someone. When your target is a sheep, do you really need to keep track of its hp? If it is badly savaged, it will likely die. If you strike it in the spine with a sword, it will likely die. What do you gain from tracking its hit points?
No one is going to start swinging swords at sheep anyway. They'd dispatch them like any other edible animal. It seems like madness to suggest that just because something is alive it needs to have a hit point rating. The only things that you need to know the hp for are things that will fight. I suppose it's not out of the question that a sheep may bite you but the real question is why are you hitting it with a sword/bow/axe and not killing it with a blow to the throat? They do not present a significant challenge.
He came around and agreed that it made more sense to treat the sheep as scenery at which point he blew my mind by telling me that the sheep in the module not only had hit points and hit dice, they also had feats and skills. Those are some talented sheep.
This attitude, towards all-codification, is very strange to me. I implore you, DMs, take the rules that make sense and ditch the rest. Modify them to be appropriate to your own table. Most of all, find players that trust you to make judgements. That's why you exist; not to interpret a schematic of rules fed into you by player action. A computer can do that. You are a living, breathing analysis machine, more capable of comprehending the world than any static set of numbers ever will be: which is, I think, well demonstrated in the problem with sheep.