This actually happened to me a few years back at the University of the Arts in Philadelphia.
My sophomore year, I roomed with a girl named Kara. She was a jazz vocalist, but her main interest was opera. We had a small room on the sixth floor of a dormitory called Juniper Hall. The walls were thin, and her late night singing and voice practices would keep me up late. After a month or so of lost sleep, I convinced her to move her late night practices to the music studios in the Merriam theater building a block away.
Around eight o'clock one evening, Kara announced that she would be practicing late for an upcoming recital and probably wouldn't be home until around midnight. Great, I thought, that means I can go to bed early (I was beat... I had a horrible day in acting studio, and was ready to pass out as soon as I had dinner). She said goodnight and left, coffee and sheet music in hand.
I made some grilled cheese and soup, gobbled it down, and immediately began to prepare for bed. By the time I got out of the shower, my eyelids were so heavy I could hardly brush my teeth. I pulled on my PJ's and crawled into the top bunk of our bunk bed. I was out as soon as my head hit the pillow.
I should take a second to describe the layout of our apartment. When entering the apartment, the bedroom was through a door immediately to the left. Our bathroom was inside the bedroom, just past the bunk beds (UArts is nice in the sense that you don't have to share bathrooms).
Anyway, I woke up to the sound of the apartment door closing. I opened my eyes, and groggily checked my phone: midnight on the dot. I rolled back over and closed my eyes. I heard Kara enter the room and stop in front of the bunk bed. Checking to see if I'm actually asleep, I thought. She flopped down on the bed below me, which was strange, as she was a stickler for brushing her teeth and washing up before bed. Then again, exams were just around the corner, and we were all exhausted. The mattress below me creaked, and then was silent. I couldn't even hear her breathing.
I started to drift off again. I was just on the edge of deep sleep when I was startled awake again by a noise.
A key in the lock. The door opening.
And Kara entering our apartment, humming an opera tune.
The mattress below me creaked.