If I am ever faced with a Half-Platinum Vow of Poverty Paragon Pseudonatural Tarrasque, I will not use my Diplomacy skill to turn it into an ally by making the point that, because it is now strongly Good-aligned, it would naturally prefer not to kill my Paladin character and her Good-aligned buddies and would at the very least stop and negotiate before biting us in half.
Also, when offering large amounts of livestock to the Tarrasque, it is necessary to actually own the livestock in question.