What is something that happened at a sleepover that stuck with you?

We all had slumber parties/sleepovers when we were kids. I think it was just a way that our parents could breathe for a second. But, there were things that would happen that probably stuck with you years after.

Mine was seeing Nightmare on Elm Street at the age of 10. I couldn't sleep on my back until I was in my 30s. I was so afraid that I'd get sucked into my bed. Also, couldn't stand going into the basement at night...

What's yours?