Since everyone's posting about creepy things I'm gonna say what happened to me.
One day I came home sick from school. I was alone except for my dog who was downstairs. I was going to take a shower and I locked the door out of habit. Before I went in the door handle went down and I heard the noise my door makes when like someone tries the handle and it's locked. I was looking almost at it by coincidence when it happened. Well I saw it peripherally atleast. Like 10 seconds later I came out and looked around, and no one was there. Unless my dog had for some reason jumped on the handle for the first time ever seen, then ran back downstairs without making any noise in about 10 seconds, there is no explanation. It's true. Try to explain it.