Suddenly you find yourself splashing in water out of your depth. Getting to your feet, you discover your head just comes up above the bubbles and the sides of the bath.
Feeling your body, you find you have wet fur. Holding your hands up in front of you, you find the fingers are long and knobbly, with long claws. You feel some kind of long tail under the water too.
A glance in the reflective taps confirms it. You've become a wererat, little more than half the size you are now!