3.5 FAQ, on Polymorph wrote:When you cast polymorph* twice in succession on the same target, does it keep any of the abilities gained from the first spell’s form?
No. This falls into the category of “one effect makes another irrelevant” (see page 172 in the Player’s Handbook). A polymorphed elf wizard who then casts shapechange wouldn’t retain any of the abilities gained from polymorph—only the wizard’s original form (elf) and new form (from shapechange, the last spell cast) matter.
*The question and answer uses “polymorph” to refer specifically to spells that rely on the polymorph or alter self spell to adjudicate their effect (including alter self, polymorph, polymorph any object, and shapechange), psionic powers based on the metamorphosis power (including metamorphosis and greater metamorphosis), and any other effect based on either of these lists.
So, yeah. Unless this is wrong, bye bye Polymorph stacking builds.
Note: This won't be the first time the FAQ is stupid. What is the "officialness" of it anyway? If the FAQ says yes and the rules say no, who has precedence?