Ok i searched and i didnt find this anywhere and i thought this was the best place to post it so.
Step 1. Wait for someone to start the part of the Onyxia chain in SW were Marshal Windsor goes into Stormwind Keep.
Step 2. When they talk about encoded tablets right click on Lady Prestor.
Step 3. Keep the little dialogue open until they get done talking and she has turned into Onyxia.
Step 4. Watch as the ppl doing the quest get very very very confused.
not really an exploit but i just thought id post it.