WHEW. Read through this entire thread. And aside from anything involving children, here is what I found interesting in the thread, for those who don't want to spend the time reading it from beginning to end:
HOW TO BE CREEPY:
Inversion: take something that is otherwise cute and associated with purity, and turn it on its head.
Mystification of the Mundane: take a commonplace event or item, and attach a strange event to it to make players search for meaning (e.g.: the party finds an old maypole, streaked with corrosion. As they approach it, the sky grows darker and the wind catches in the tattered banners.)
Reversion: erode feelings of control by undoing what the players have done (e.g.: the party has found an old dagger on an altar, and pick it up. The next time they look back at the altar, the dagger is still there, the altar undisturbed).
Progression: build a sense of foreboding (e.g.: an old, faded tapestry hangs on a wall. In the torchlight, it appears normal, but when viewed from shadowy illumination, faint traces of silver can be seen. By dimming the lights, the players can see these silver lines growing brighter and sharper. The process is reversed once light is applied, but starts up again when darkness falls. If they watch it in the darkness, the lines shift and flow, forming an archway - and a figure seems to loom within, head bowed in shadow. The figure slowly looks up).
Communication: cryptic messages, especially connected with the unknown (e.g.: a locked door in the back wall of an old, abandoned cellar is made of warped wood, and covered with flaking paint. As the party works to open it, the pain slowly flakes away, revealing a scrawled word: "No". Will the party still try to open the door?)
Omni-sensory Perception: Use all the senses, half heard voices, fleeting images, the smell of flowers wafting, the smell of deep earth and rain on stone. A wall slick with fat. Use their associations, and turn those associations around.
Some very creepy elements to add into your games:
(or "The Random Creep Table")
1. spewing, wriggling maggots (or giant, hairy maggots, the size of small ponies, indifferent to the PCs)
2. strange, ubiquitous buzzing of flies
3. strange-looking bag with splotches on it, the skin of human-being with all the stuffing sucked out except for desiccated bones & organs
4. glimpse in the mirror of a grayish humanoid form leaning over PCs even though nobody could see it, and caressing the back of one PC's neck with a tentacle. It disappears from the mirror as soon as PC raises the alarm
5. invisible, intangible webs, which were moving very gently in a non-existent breeze
6. victims turned into wights while still alive (still had a soul and still aware of what's going on)
7. a vaguely humanoid mannequin made of stitched together flayed human faces and filled to stuffing with maggots; if hit with a slashing attack, it spews maggots on PCs from the wound, which burrow into their flesh; it can also grapple one target and vomit maggots in this face and eating him alive
8. tower bell starts ringing, causing the PCs' vision to blur and sense of hearing to distort; they eventually black out for a moment from the vertigo and see everyone around them as corpses
9. vision/dream of an "operation" on a homeless beggar in which his torso was cut open; a live, mangy, squirming rat was placed inside and sewn up with ragged leather stitches. Later, swarms of rats erupt from the pipes all around them
10. a black longsword with leering daemonic faces on it that seem to shift and mouth obscenities out of the corner of the PCs eyes (anyone who picks it up hears those obscenities in his mind as blasphemous voices that attack Resolve at +3 every round he holds the sword, and feels the sword biting his hands, slicking them with blood
11. touch an evil altar & receive visions of death, oblivion, and writhing tentacles, but the PC kinda likes it and feels that he might want to touch the altar again
12. dozens of chains hanging from the ceiling and softly swaying and chiming in the breeze, moonlight coming in through the broken windows, dark stains on the floor beneath the chains, an eerie silence except for the clinking
13. crates of black bone, pulsating with scarabs picking them clean
14. harvesting mushrooms that bleed
15. occasional sounds of voices, footfalls, drafts, feeling like someone watching you, and light tugs on clothing that no discernible thing had caused
16. worm spies
17. human-faced grubs
18. the ceiling writhes: bats! (or fledgling vampires?)
19. disembodied heart on an operating table...it starts to beat!
20. paintings that look like black swirls that bulge like something is trying to break out
21. phantom hands reach out and touch the PCs at random intervals as they walk down a hall
22. every time PCs encounter a dead body, a small black beetle appears out of the corner of the eye and scurries away in a few seconds, so they can't catch it (then have it appear when they go to a place of safety)
23. fog that seems to make "shapes" that only one PC sees before it disappears
24. A fleshy bottle, somewhat hairy, and no stopper – the neck is held shut with a sphincter and by stroking the bottom of the bottle gently, the sphincter opens
25. decapitated head sprouts legs and walks away
26. shadows not in synch with the movements of their caster
27. any torch, flame, candle, fire's shadows always showed to be blowing away from a character no matter which way the wind was blowing (if any)
28. Those who use Detect Evil pick the target up as 'flickering' evil and not evil, if they make a rather high Listen (or Notice, depending on the game) they will realize that the flicker is in time with their own heart beats.... Those with Detect Good would notice the exact same thing
29. a mirror that shows what the viewer will look like at the time of death (e.g.: "your reflection looks much like your normal reflection... only you're missing your eyes and your hair is slightly longer")
30. a tiny, animated rag doll stands staring at you with little dead black eyes (the PCs follow it into a ruined bedroom, where it lays down on an old bed next to the remains of a long-dead child, and go forever still
31. a town full of petrified (literally) people, or a town so recently deserted that cups of coffee are still steaming
32. anything with an alien look that moves slowly and languidly, an uncaring, drifting, unthinking danger drifting along with no set course (think ghost jellyfish)