In a nutshell, this is a setting with an exaggeratedly 'Halloweeny' theme.

It's a setting that usually has a variety of horror monsters as the inhabitants. Expect the sky to be perpetually night or overcast, and the buildings to be a dingy gray. The water is often a vibrant green tone. The main colours are usually black, gray, orange and sickly greens. Despite these somber colours, this setting is not played solemnly. Imagine the Perky Goth character as a setting, and you've got this place.

This kind of setting is not usually scary, or at least not intentionally so. It's intended to be somewhat playful and fun. A good well to tell if a series is set in a place like this is if there are jack-o-lanterns and it's not Halloween, although it's not a prerequisite.

Named for the main town in The Nightmare Before Christmas.

Examples:

• The Trope Namer, the aforementioned Nightmare Before Christmas, along with it's spiritual successor, Corpse Bride
• The Halloweentown series of movies, notably the titular town is unusually bright and cheery.
• The Addams Family, along with the similarly themed show, The Munsters
• Ruby Gloom is set here.
• Casper's Scare School has it's school here.
• A popular setting in video games. Haunted House on the Atari is one of the first arguably set here.
• Super Mario World has an unlockable skin that turns the game into this is you can beat the special stages.
• Pumpkin Hill, Aquatic Mine, and several other levels in Sonic Adventure 2.
• Mad Monster Mansion in Banjo Kazooie
• The entirety of Luigis Mansion
• Niffleheim in the somewhat obscure MMO Angels Online

Up for grabs