[3.5 or PF] Active Spells, and Targets Ceasing to be Valid

[The Grue]

What happens if a spell is cast on an object/creature, and then, before the spell's duration expires, that object/creature is altered in such a way as to be an invalid target for the original spell?

Practical example: A 16th-level Wizard casts animate objects (http://www.d20pfsrd.com/magic/all-spells/a/animate-objects) on a small rubber duck. He then casts polymorph any object (http://www.d20pfsrd.com/magic/all-spells/p/polymorph-any-object) to transform it from a small-sized object to a colossal-sized object. Is animate objects still in effect, even though the duck is now well beyond the size limits of a 16th-level casting?

Possibly better example: First cast obscure object (http://www.d20pfsrd.com/magic/all-spells/o/obscure-object) on the rubber duck, and then animate it. Is the duck still hidden to scrying(or alternately, is it both an object and a creature at the same time)?

A similar 3.5 example could be drawn up using Polymorph, but you can probably just use your imagination there.

[Arael666]

From SRD


Spells or magical effects usually work as described, no matter how many other spells or magical effects happen to be operating in the same area or on the same recipient. Except in special cases, a spell does not affect the way another spell operates. Whenever a spell has a specific effect on other spells, the spell description explains that effect.

That's all I could come up with.

[The Grue]

Hrm.

Well, guess it's time for the consolation prize: find a hilarious way to break the game by abusing this!

Anyone got any ideas?