In The Goblet of Fire, fake Mad-Eye Moody Transfigures Malfoy into a ferret and bounces him up and down, to "teach him a lesson".
In The Tales of Beedle the Bard, Babbitty Rabbitty and her Cackling Stump, Dumbledore comments on the difference between an Animagus and Transfiguring oneself into an animal:
Animagi do not retain the power of human speech while in their animal form, although they keep all their human thinking and reasoning powers. This, as every schoolchild knows, is the fundamental difference between being an Animagus and Transfiguring oneself into an animal. In the case of the latter, one would become the animal entirely, with the consequence that one would know no magic, be unaware that one had ever been a wizard, and would need somebody else to Transfigure one back to one's original form.
How then did Moody's Transfiguration work? Wouldn't Malfoy have lost his human consciousness during his time as a ferret, thereby defeating the entire purpose of the teaching moment?