I started staying the night over at my girlfriend's house when we were just friends. The first time was a few years ago, when we were both freshmen in high school. Since we were just friends, she set up some blankets and a pillow on a futon on the ground for me to sleep on.
That night after we had gone to bed, I woke up in the middle of the night, because sometimes I just do. Usually, I just go back to bed but this time it was different. As I was laying there about to fall asleep, I felt something push down on the futon next to me. I thought it was one of her cats so I didn't mind it. Then I felt it brush up against my hair. It almost felt like a hand petting me so I freaked out and jumped up and turned on the lights. There was nothing there. I checked her whole room for the cats or her dog but they weren't there and her door was closed. I left the light on the rest of the night because I was afraid. I was considering waking her up, but I didn't want to bother her.
That was the first time I ever spent the night at that house and the first time I ever experienced anything there. That didn't stop me from spending the night again, though. And there have been plenty of other experiences also. Read my other stories if you want to find out.