I was at school one day, and I really, really, needed to use the bathroom. There was just one problem with that - I was on the sixth floor, and nobody uses the sixth floor girls' bathroom because rumors had it it was haunted, and I wanted no part of that. But this was urgent - I needed the toilet very badly. So I shot down the hall and into the bathroom, and immediately locked myself in a stall and, uh, "did my business".
Then I heard the door open and close quite clearly but very softly. Then I could hear tentative footsteps crossing the room in my direction. I thought nothing of it; it was just somebody else who needed to use the toilet. But as I bent down to pick up my pants, I saw under the stall door that there were no feet to match the footsteps.
The door of the stall next to me creaked open and shut, and there were more footsteps. I listened and heard the rip of toilet paper, the flush of the toilet, and the stall door opening and closing again. Yet I never saw feet in that stall either.
There were more footsteps, and still no feet. The footsteps went to the sink right across the room from my stall and the faucet turned on. Surely if there was anybody there I would be able to see their feet at the sink. I peeked under the stall door. No feet were to be seen.
More footsteps. The door opened and closed. I got out of my stall as the door was swinging shut and saw no one there - no flash of hair as they turned, no heel peeking by as they walked away. And mind you, the door was approximately 3/4 of the way open when I glimpsed it.
The room was also filled with a barely noticeable but definitely there milky whitish fog and was a little chilly. I never went in there alone again.
P.s. A few weeks after that, my friend and I left our backpacks inside the same bathroom while we retrieved something she left in the library. When we returned, our bags had been moved across the floor. It was weird since barely anyone used that bathroom and our bags hadn't been in the way where the were before. Strange.