"I know you're doing it." Jessica told you, as you stopped touching your new hair. "Well... It would be awesome if I was as high as you, and if I was as strong as fast you..." She continued. You knew she was begging for some of your traits, so you decided to give them to her, you could always reverse them, what could go wrong? You went on to think about your sisters height, then your muscle on her. The same feeling rushed through your entire body, you definitely felt yourself lowering but didn't want to open your eyes.
You felt that you weren't lowering anymore, and decided to open your eyes, the moment you opened them you suddenly saw how big the world was, you were barely taller than the bed! Then, you saw the beast of a six year old that Jessica was, you just barely reached up to her crotch, you were looked, wide eyed around the room as Jessica was flexing her new muscles.
As you stopped being mesmerised, you realised your old clothes were too big, meanwhile Jessica's skirt was ripped to pieces once she expanded, you quickly climbed out of the shirt which was nearly as big as you, and went out of the puddle of jeans. Jessica was naked, when she came to realise that, and that you were staring at her vagina, she quickly went over to you and covered your eyes, knocking you over with her new power on the process. "Oh god, I'm so sorry..." She quickly started apologising, you just shrugged it off, you were incredibly fragile.
As you two were talking you realised how funny it was to see your sister so huge but still with her voice, your sister pointed it out when you started laughing halfway through her sentence. You quickly switched that as she said that she would punch you if you laughed. So there you were, on the floor, still talking, both naked. "We should probably get dressed." You proposed, that tiny voice coming out of you was incredibly alien. "We might as well swap everything, you look so weird with your beard on my body." Your sister mentioned. "You just want my penis!" You exclaimed, laughing.
"Fine." You say as you began the process of swapping. You felt your face as if it was weathering away, being chiseled. The groin was the worst part, it felt like a Hoover was being shoved up your intestine. You felt the swaps finish, not wanting to see if you were your sister yet, you quickly ran into the room to put something on. You find a flowery dress, you put that on the floor and find panties, an undershirt and some tights. You quickly put those on, then put the dress on. You now stared into the mirror. Sure enough. Your sister. From the hair to the painted toenails.
You rushed into your room, and saw that your sister was now putting on her jeans. She looked at you. "Can I... Like... Punch you? I wanna see the power!" She shouted, "no!" You shouted back. She was ripped with muscle, she could kill your fragile self with a single punch. She was advancing onto you. That was the limit, you started turning back into your old self. You closed your eyes... But felt nothing. You opened them back up. You saw her muttering. Then going up to you. "I can repel the effects!" She shouted. Now running up to you, you felt a straight punch in the stomach, knocking you clean out before you could say anything.