Trying it on his sister Sara

Who else could be a better test subject than his sister? She was quite hot and conveniently taking a nap in the living room right on the couch infront of the TV. He checked whether anyone else was near - everyone else seemed busy, so he was good to go.

"Alright, now... what will I do... I could swap one small part to test it first... or... perhaps, it doesn't matter if small or not. I always wanted to do this kind of stuff... this is my dream... I can't believe this is true now. This is just a stupid prank, and I am even more stupid to fall for it.", he whispered to himself while looking over his sister's sleeping body.

Suddenly, an idea striked his mind. He always was interested in how other body parts and bodies would feel, however... what about unmatching parts? What if he swapped his hand for his sister's foot?

He felt himself getting hard at the possibilites. A part of him was disgusted by how weird and fucked up his mind was, but the greater part was overcome with curiosity. The possibilities were ENDLESS.