When I was like 13, my bed I've had for ages broke, so I was sleeping on the floor until the next week when I was able to get a new one. I was sleeping with my feet facing my bedroom door so if I sat up, I'd be staring at the door.
I woke up in the middle of the night, around 2:30-ish to scratching at my bedroom door. I sat up and stared at my door and scratching intensified. Then the door suddenly slammed open and closed almost immediately, the neon green glow of my alarm clock showed nothing behind the door when it opened and I was scared shitless. I do have a dog, but she'd have to go through my parents bedroom door, and the stairway door, so not possible.
When I was even younger, I'd often get this feeling, of not being quite myself I guess you can say, when I would be trying to sleep and my bed would start to shake, not softly, but not violently either. I would also hear voices that sounded like it was coming from a walkey talkey or something and foot steps going up the stairs.
Before anyone claims "Oh this was sleep paralysis." It wasn't. I know what sleep paralysis is, and I've had it twice, those times were not it since I was able to move around and talk