Just to add my own thoughts on this interesting idea. "Save the good dragon from the evil princess"
The dragon in question does not have to be full grown. Imagine the evil princess holding a dragon egg or hatchling ransom to force the local dragon population to do her bidding.
To adapt this to a forest scenario use a faerie dragon protector of an ancient forest. Or even have the whole thing be an illusionary romp caused by the dragon!
Lastly, imagine the evil princess gaining control of the court wizard's psuedodragon familiar. This is possibly worse than ransoming the dragons depending on the wizard's level!