Under the special advantages/disadvantages, the choices for "Bonus to Hit" and "Phobia" have four choices: Animal, Undead, Daedra, Humanoid. I'm having trouble because there are many enemies that I can't figure which category they fall into. Undead and Daedra are easy, but there are many I would call Animal only because they don't fit anywhere else.

1. So do all enemies fall into one of these 4 categories?
2. If so, what are centaurs, gargoyles, werecreatures, harpies, etc? I pegged them all as animals, but I'm not sure.
3. Or there is an "Other" category you just can't choose as an option?

What I'm really asking is: is there a definitive breakdown of the enemies regarding this?

I don't have any choices on my disadvantages. For example, I'm given disease for critical weakness. I believe I'm on Daggerfall XL. Can't tell for sure because I'm at work on my phone.

I would say that anything that's not clearly a person falls under "Animal", but thinking about it again, the term "Humanoid" is really ambiguous. UESP's Daggerfall Bestiary is divided into more categories than those four, but all the "Human" enemies are listed as "Humanoid". Though that probably doesn't help you much.

OK. So I suppose the answer is "Nobody really knows"

I cannot find my Daggerfall Chronicles. (It must be sitting in a box somewhere), but I believe it may be mentioned in it. If I find it, I'll check it out.

I just check mine, there isn't anything mentioned in it about the monster type, and doesn't even have anything about custom class advantages/disadvantages.

Yeah, I had checked my Chronicles, too. Prima's doesn't have anything either, but it doesn't ever really have hard facts anyways.

I was hoping someone with a better understanding of the code (interkarma!) would pop in...

Sorry Jor, I have to admit I don't know on this one. I'm guessing there will be a value in monster.bsa (possibly in the .cfg records) that defines enemy types in relation to hit bonuses and phobias, but it's not something I've looked for. It might be a fun experiment some time to pattern-match the obvious groups (undead and daedra like you said) and try to work this out. I could also be completely off the mark here and this classification is stored elsewhere.

If I get time down the track, I promise I'll have a shot at this for you.

No worries. If it comes up, that'd be interesting to know, but it's more of a curiosity at the moment.
But, it's still something we don't know about Daggerfall, so that must be remedied!