When I was 18, my parents went on vacation and left me home with my 10 year-old sister for a couple days. Which was totally my choice.
I decided to take a shower. My sister was watching TV in the living room. So I went to the bathroom and took off all of my clothes. Just as I'm about to step in, my dog, who's outside at the time started barking like crazy. I put a towel around me and ran outside to see what the matter was. It was the guy I had a crush on, standing in our driveway. He looked happy to see me in a towel. We started talking. About five minutes into the conversation, my sister came outside. I introduced her to him. The towel I was using was specially made for her, that she always whined and complained whenever anyone else would use it. She turned to me and got a really angry look on her face. "That's my towel!" she shouted..
Just then, with my crush standing there, my sister grabbed the towel, leaving me naked. She ran into the house with it. I ran to the door totally naked. My crush saw me in the buff. I was beyond mortified. To make it worse, she had locked the door. I peaked in through the windows and saw her standing there laughing. My crush was also standing outside still looking at me. He pretended not to be looking, but I could tell he was. I covered up what I could with my hands as I ran around the house to the back door. Our neighbors, were having a pool party with a bunch of 14-15 year-olds. They all saw me and started laughing. Still, I managed to open the door, put on some clothes, yell at my sister and apologize to my crush.
Just wait till my sister enters high school. I'll find someway to embarrass her.