You look at the jellybeans and at your sister, then back to the jellybeans. It couldn't hurt to try a little more, could it? Carefully, you reach for a pink jellybean with an A on it, guessing based on the previous one that it must change you in parts and this is "arms". Unbeknownst to you, there is a faded B on the jellybean you don't see.
As you chew the jellybean and swallow, a tingle passes through your body. You're alarmed when the first thing you notice isn't your arm changing, but your hair growing out and getting in your vision. "What the-" you break off your exclamation and your hands fly to your throat as you realize your voice is now a couple octaves higher than normal - the voice of a girl. Suddenly you feel pricks on your skin and pull your hands away to see the nails growing as your hands grow dainty and slender. The change continues to your arms, which grow slender and smooth to match your hands. Turning, you hurry to the bathroom; whatever happens next, you want to see it.
On the way to the bathroom you stumble as your shoes come off, sliding easily off of feet that are now far too small for them. By the time you get into the bathroom you're grabbing at your pants to hold them up as your legs and waist slim down. Then you regret the action when you feel a pressure growing as your hips widen with a disconcerting cracking sound. You quickly try to pull your shorts off, but now you feel your butt swelling into a feminine shape, making it harder. Finally you get your shorts and boxers down and kick them away, almost staggering into the wall as your new proportions throw you off-balance. You straighten and face the mirror in time to see the next change.
Above your new, smooth, toned legs you see the shaved mound of your new, feminine opening, and you can feel movement inside you as your organs rearrange themselves to complete the transition from male to female reproductive facilities. Pulling up the hem of your T-shirt, you watch as your stomach flattens and smoothes out, becoming toned and losing the more obvious musculature from before. The tingle of change moves to your chest and you see two mounds rising in your T-shirt. You stare in awe as the mounds swell, their tops becoming more defined as your nipples swell and harden with the pleasurable change. The shirt begins to stretch, showing the curvature of your growing breasts as they transition from mounds to the more rounded forms of full breasts. The shirt had felt loose on your narrowed frame before, but now it felt tight again - at least in the chest - and you hoped the change would end before it got unbearable. Fortunately, it did, leaving you with a sizeable pair of breasts somewhere around the C-cup range.
You stare into the mirror, seeing the body of an attractive girl who could almost be the twin sister of the girl you had left out on the couch. You have completely changed almost exactly like your brother. What do you do?