I've had loads of creepy stuff happen over the years but this occurred at Halloween itself about ten years ago, so might be most pertinent!
I was on my way home at night. Late-ish about 11. I lived in Tottenham at the time in a street filled with Victorian houses with deep front gardens. There was something about that road that made me jumpy at night at the best of times, there were lots of Plane trees lining the road which gave off creepy waving shadows where the street lights broke through the leaves, and even though near the tube, there never seemed to be many people walking along.
I'd come back from a night out where there were plenty of people out and about celebrating and wearing costumes and the difference to that cold dark street seemed very noticeable.
So I was alone on a seemingly deserted road when out of one of the deep front gardens ahead of me, which was bounded by a tall hedge, walked a child. I would say about 6 or 7 going on height and very slightly built, wearing dark trousers and a hoodie. Definitely not a small adult, everything about the walk and way they held themselves seemed like that of a child. You know the way some children are slightly tottery? Like that.
They walked away without seemingly noticing me. I was taken aback - the house they had come from was completely in darkness as far as I could see and no adult followed them. It was late at night - what were they doing out alone at that time? I actually stopped for a second or two to look for a parent as it seemed out of place - not a particularly safe area late at night, even the local little oiks ran in packs of two or three. I saw no one, so on I went, watching the child the whole time.
I was wearing trainers and was aware that my feet were making little or no noise on the pavement. I didn't want to startle the child so I coughed lightly. The child stopped and turned to face me. Slowly.
That was when my skin felt like it was contracting all over my body. The child was in shadow, under a tree by a lamppost on a dark road. It appeared to be wearing a mask, but not a classic cheapo supermarket type Halloween plastic mask. More like the silicone pull over your head type. I couldn't see what it was exactly, but it seemed like a wizened, shrunken, deformed zombie mask. But as I say it was in shadow under its hood. It was enough to give me the immediate horrors, though. I stopped in my tracks and we stared at each other. The child was preternaturally still. No movement at all. And then very slowly, it tilted its head quizzically at me as if to say "who are you?"
I was properly sweating by this point. My rational brain was shouting at me that it was just a child, albeit a very odd one, to be out at this time -but my lizard brain was shouting louder to get the hell away from this horrible little thing. We must have stood staring at each other for fifteen seconds or so.
And then it did the weirdest thing. It reached out to the lamppost and curled its hand round the pole, swinging its body backwards and forwards gently for a few seconds in an almost playful fashion. I honestly felt rooted to the spot. I felt sick. My heart was hammering. And then it leaped, fast and nimble like a monkey onto the post itself, and pulled itself up until its feet were on the slightly wider bottom part, so it was hugging the trunk of the lamppost. I still couldn't see its face properly as the overhead light was casting onto the top of the hood but it just hung there, a bit higher than my head, looking at me, saying nothing.
I inched past it, one step at a time, keeping my face towards it at all times. I had the most tremendous urge not to turn my back on it for an instant. It stayed still, just turning slightly to watch me as I moved. I kept backing away until I was about three yards away and then I turned and ran. I didn't look back, just ran as fast as my fat little legs would carry me till I got home. Fumbled the key into the lock, went straight upstairs and looked out of the window down the road to where I'd been, but there was no sign of anyone, child or otherwise. Thankfully my then boyfriend was home, so I gibbered at him for a while (he clearly thought I was nuts).
If that was a child (and I really hope it was), it had an incredible sense of timing and theatre to think of freaking an adult out like that. And if it wasn't- urgh, I don't want to think about that. 