You already know the drill. The witch takes out the cork of the potion flask and hands it to you. You open your frog mouth and gulp it all. The taste is awful; by far the worst of them all.
You just keep there, however, expecting fro the changes to come quickly.
"GRIBBIT!" You involuntarily croak loudly. Your air-sac expands but doesn't go back to normal. All of your body begins to feel bloated, your belly begins to bloat too and before you notice it you are turning into a ball of slime, as your skin keeps producing it. Your skull starts to hurt a great deal and that's when you realize it's becoming human again. You can hear the witch and the sleazy client giggling as if you're nothing but a horrendous show. Your posterior paws retract inside you, your torso turns into a human torso and becomes separated from what's transforming into a mollusk's foot. Your whole body starts producing a thick disgusting slime and when the pain and discomfort finally subside you realize what you are: from the waist up you're a human with slimy skin and form the waist down, you're a slug.
When you think you are finally done. Something very weird happens to your vision as it blurs out for a moment. Your eyes come out of their orbits and dangle. The witch and the client burst out laughing. They then become more consistent and you realize you have eyes like a snail.
"Well isn't this one marvelous? What a disgusting creature this is. I believe we have a deal " the client happily said shaking the witch's hand. She ignores you for the past moments while hse sells him the potion and wishes him well in his villainous plans. You stand there trying to sort out what's your best move, realizing it just might be waiting.
The witch finally closes the door and turns around. She looks a bit surprised as she looks at you.
"Oh yeah...what do we do to you now?"