Dan barely had a moment to protest against his sister, before he started to feel strange. All the hair on his body receded. His body was shrinking and becoming scaly all over. It was getting harder and harder to breathe the longer the transformation took. Dan thought that a handful had minutes had passed, when realistically it was only A minute. Everything happened very quickly, while his sister watched with sadistic glee. He didn't even notice that a fish tank was under him until he fell into it. He could breathe again.
Kat watched it all as she licked her lips. She couldn't wait to cook his brother, now a fresh fish. She could see Dan slowing taking in his new form and smirked when terror shone on his fishy eyes when he realized what she had been planning. Both sibling new how much their parents loved seafood, especially fish dishes. Even more when they could catch it fresh.
Dan could only imagine what kind of dish Kat had planned for him and none of it would be fun for him. He isn't sure he would even survive the experience. He hoped his sister at least knew a spell to keep him alive. Though would the torture of being cut, gutted, de-spined, cooked, or whatever Kat planned be worth living through it. His only chances were that his mom would disapprove what Kat had done.
He looked at himself more carefully to get a better idea what fish he was and what potential dishes his sister would make. The possibilities were endless and a nightmare to come.