A lesson

Jake had felt a little tricked by his sister. She asked him if he'd help her pass her finals, and he said, "Sure, anything you want." Just the words she was looking for as she cast a bodyswap spell, which could only be done after both parties agreed. He had spent a week in her body, passing her finals. He didn't like how he was tricked, but knowing to swap back, the parties had to be willing again, he figured he'd refuse. Just to teach his sister a lesson.