Walking down into the washing room you see that your sister has leave her sleepover clothes out to dry. You check the dark pink shorts and light pink singlet and find they're dry. Meaning it likely won't be long before you sister comes to collect. You should really just leave them and get out of here while you still can but a part of you is tempted to go through with this wild idea.
If you manage to look like your sister and delay the real her, then maybe you'll be able to fool her friends and make it into the slumber party for just a little bit. Until your sister returns of course... But...
You're tired of being make fun of for your relative short statue and slim figure for a boy. And if you back down now you're going to be branded a wuss for the rest of your school years. Taking a deep breath you smuggle the clothes into the near by upstairs bathroom.
Making sure the door is shut, you take off your clothes, including your underwear. Then you begin put on your sister's clothes. First you put on her panties and bra, causing you to blush yet also shutter at what your sister would do if she found out. A part of you wonders if this part is necessary but you decide if you're going to do this you might as well go all way.
Then goes on the shorts, managing to fit on okay although they obviously aren't made for your figure. Then goes on the singlet. Her clothes are too small for you in some areas while also too big in others. Being obviously made for a 18 year old girl.
"I can't believe I'm doing this." You say as you see how you just look like a boy wearing pink nightwear.
"I'm never going to fool her friends like this."
Looking around the bathroom you hear no sign of your sister returning, meaning you have time to choose your next move. Maybe you should just quit while you still have your head. Or maybe you should keep going..