I did not think there was a crime heinous enough to deserve this place as a sentence..
"Zutul? You mean someone took time to give it a name?"
Maj. Rielle Law
If a creature is transformed into another creature (say, a human into a dog), then that creature will become more and more accustomed to the new form until a point is reached where reversing the spell is impossible. A second transformation is possible, but the creature will have to go through the whole process again.