Saw recently that the improved polymorph debuff is actually a buff.
Improved Polymorph - Spell - World of Warcraft
Turns out that you can actually just click it off like you would do to any normal buff that you have on yourself.
Uploading a video now but it is taking forever so..
Edit:
http://www.youtube.com/watch?v=rmbP-ly30MQ
Steps:
1) Get polymorphed
2) Get damaged
3) Get stunned from improve polymorph
4) Right click stun debuff
5) ????
6) Profit.
Go nuts!