Animal Growth with Animal Companions

[Derren]

The spell Animal Growth doubles the HD of an animal. What happens when the spell is casted on an animal companion whose HD now exceed the maximum number of HD of animal companions the druid/ranger can have?

From a look into the MotW it seems to me that this is supposed to work (But there is no rule concerning this in it).
If asked now I won´t allow it (better if the HD goes over max the animal wouldn't´t follow the orders of the druid and would flee), because with the "normal" buffs the druid in my group casts on his dire wolf, the wolf becomes as strong as our Barbarian of similar level as the druid. With this spell in addition, the wolf would surpass him by far.

 

[Crothian]

The HD limit is not effected by temporary effects like this. So, Animal Growth away.

 

[Dingleberry]

Unless, of course, you've taken the seemingly obvious step of casting awaken on your animal companion, in which case animal growth - arguably the best spell to apply to an animal companion - no longer works because the critter's now a magical beast.

Irritating.

 

[James McMurray]

What happens when the spell is casted

Actually, nothing would happen, because "cast" is the past tense of "cast". It is impossible to have a spell "casted".

However, going by the spirit of the question I would agree with those posters who say it does not have a deleterious effect. You still have the animal as a companion.

Sure, it means that a druid's companions can get pretty buff, but can that Dire Wolf now fit in a dungeon situation when it becomes huge? Also, a single dispel magic will turn that wolf into puppy chow. You only have to do i once to make a druid think twice about using his animal friends as frontline combatants.