Sneak down and open a present

You make sure to get up early to sneak downstairs and open a present early before anyone else awakes. Looking under the tree you sieve through the presents to find one with your name on it when you get the idea to open one of your sister's instead! Genius! You pick out a small one then she won't notice it's gone and rip it open. Inside you find a... vibrator? Who on earth got your sister a vibrator for Christmas? You open it up and flick the switch on it as it begins to vibrate, you analyse it in your hand, still curious as to why someone would gift this when you suddenly drop it. The vibrator happens to fall down into your boxers, and you fall to the floor in pleasure as it makes your whole body tense up. Your penis being next to the vibrator makes you feel almost orgasmic, you gasp in shock when you feel the toy wiggle inside you! How could this be possible? You pat a hand down there and you can't feel your dick, it's gone! You tilt your head back to try and deal with the pleasure as hair explodes out your head and turns a bleach blonde colour. You reach a hand up to your chest as your nipples become more sensitive and breasts begin to bud from your chest. You continue to moan with your new feminine voice quite loud now. Your boxers become panties as the final transformations are complete. You lie on the floor exhausted as you lock eyes with your sister, who's been watching you the whole time. She seems pleased with your results.