This one may just be the best written of the pastas on my list, and for me good writing goes a long way. However, that's not what makes this story so creepy.
Disney has actually abandoned some of their resorts and amusement parks, which lends a lot of credit to this story. The second you start reading most Creepypastas you're already a bit skeptic, but not with this story. Up until the ending, there's nothing to suggest that this story is absolutely fictional, and it makes you wonder about the dark side of such a cheerful, family franchise.
This is actually the first in a series of stories in the AbD line, with both a prequel and two sequels for all your creeptastic needs. I won't spoil anything for you here, but its well worth your time to check it out.