Dan's arms were the first to retract into his body. He had been waving them around, trying to reach out to his sister. All he could do was watch. He felt his bones melding into his muscles. Next his legs joined his arms, as they retracted into his body. He lost his balance and fell into his clothes, which hadnt joined him in the shrinking. Nude and limbless, he watched his body darken a bit.
Kat walked over to reach into Dan's clothes. She pulled out the partly transformed Potato slash brother. Without a word, she carried it into the kitchen as she planned out what she wanted to eat.
Dan saw light as Kat pulled him out of his clothes. He screamed profanities at his sister, but she either ignored him or didnt hear him. His hair started to turn into sprouts on his body. It didn't take long for Dan to figure out what Kat had changed him into. Dan was speechless as the final changes happened.
Kat reached the kitchen and placed the potato on the counter. Then started walking around the kitchen to get other ingredients to add to her dish, including more potatoes. Placing them around Dan's potato form, as the final changes happened. It was now impossible to tell him apart from the rest.
Dan looked around surrounded by other potatoes. He knew that Kat would enjoy cooking him. And whatever tortures the prep work would do to him. But he couldn't get away, even if he wanted to. He is just a potato.