Disneyland Paris has a remixed Mansion called Phantom Manor, which has a continuous storyline where a young bride undergoes Rapid Aging and dies. Fun.
Even more, Phantom Manor and Big Thunder Mountain are both involved in the same background plot. It makes the roller coaster feel somewhat creepier, especially when you're on the section of ride that is right across the water from Phantom Manor, so that mining camp at the base of the second lift hill with donkeys braying for water and a screaming miner inside one of the shacks, and a goat pulling on a work shirt, might seem a bit spookier.
And paintings, revealing that the assumingly happy people are seconds away from gruesome demise (sinking in quicksand, standing on an explosive, tightrope walking above a hungry crocodile)??
It doesn't help that in that same room, after the Ghost Host implies that there's no way out, he says, "Of course, there's always MY way..." The lights go off, and suddenly lightning flashes above to illuminate A ROTTEN CORPSE HANGING FROM THE RAFTERS. And then a loud scream, and the sound of bones hitting a floor and breaking. Ughhh...
The Bride. You ascend into the dusty attic where a tinny piano plays an Ominous Music Box Tune version of "Here Comes the Bride," and you can hear a deep, sepulchral heart beat ever so slowly. You pass by a picture of a married couple, and then another - wait, is that the same girl as before, only now she's got an extra string of pearls and two dead husbands? This repeats TWICE?! And then you round a corner and there she is, in a decrepit wedding dress, smiling sweetly as she brandishes a glinting hatchet at you...
At that point, spinning around and flying out the attic window is practically a godsend.
The climax with the fireplace... there was also something about the ringing telephone in the middle of the empty secret corridor.
The split second shot of Eddie Murphy's face rotting in a mirror.
The video game carries on its source material's tradition of creeping out those who play it. The whole game has a general air of suspense as you walk down dimly lit hallways with only your lantern to guide you, worrying about enemies leaping out at you, but here are some specifics:
The introduction of the Stringy-Haired Ghost Girl enemy, which you see for just a split-second before she disappears around the corner. When you follow and manage to catch her...
Atticus Thorn isn't very scary looking at first glance, but when he promises, "I'm watching," he's not lying. After you light up the Winter Garden, you see him watching you through the glass before flying off, leaving you with some serious Paranoia Fuel.
The Mausoleum. Going down a very dark passage, hearing several loud sounds before a swarm of bats flies past you and out of the area. Then you go down into near pitch-blackness, which is why you fall into the ankle deep water, leaving you walking around in a dark, ominously quiet area with no visible way out.
The knight enemies can be very frightening if you see them running down a dimly lit hallway, wielding a very large ax that they intend to use on you.
The Children's Room. It's a long room with a door at the end. After fighting past the usual enemies, you open the door to find a mere closet. After going inside you inspect every wall. Just when you begin to think it's just a closet, the door slams shut, and the back wall recedes back. As you step forward, Madame Leota tells you to run in a panicked voice. Then something starts swinging its scythe at you, which you soon find equals half your health bar.
In Garry's Mod, someone created a map that is a surprisingly accurate recreation of the ride, complete with several working props, an Omnimover track, and sound effects. One thing you can do in the game, however, is jump the barriers keeping you from the front door of the house. Within is a small corridor with another door, but trying to walk down it will trigger you falling through the floor to an instant death, accompanied by a hideous cackle.
The mod also includes a few of the "secret passageways" through the mansion, containing control systems for the ride. However, one such passageway features a bloody room with a table and laser that is very much out of place in the Haunted Mansion, which makes it even more eerie.
On a similar level, someone managed to recreate the ride in Second Life, and also managed to hybridize the two American and Japanese versions. But what gets creepy is that once you reenter a room after going through it, it is completely empty. And this can get disturbing if you try clibing the grand stair case, only to fall through the floor and end up Buried Alive.
Mystic Manor at Hong Kong Disneyland is generally awesome and funny, but it has its nightmarish moments as well.
In the Greek/Roman room, a portrait changes into Medusa with flashing red eyes.
In the Tribal Room, the lava god was pretty cool, but the original one was terrifying.
The samurai trying to execute Albert in the Arms and Armor room. Fortunately, Albert ducks his head back in the cannon before the katana reaches his neck. There's also a suit of Mongolian/Japanese Armor holding up several helmets impaled on a spear and laughing. It's easy to imagine what he's done there.
The giant Venus Flytrap turning to eat the riders in the Solarium.