One of the most exciting elements of Imagineer Christopher Merritt's astounding, essential Marc Davis in His Own Words — a two-volume set of one of Disney's most storied Imagineers, whose contributions to the Haunted Mansion, Pirates of the Caribbean and other rides cannot be overstated — was the revelation that there was a fully prototyped ghost for the Haunted Mansion that appears to have never been put into production.
The ghost — the "squeaky door ghost" — is a cartoonish maid who is applying oil to the hinges of a door, in order to add a squeak to them.
Squeak was discovered in the background of a photo taken during production and design on the Haunted Mansion and later matched to Davis's sketches. This all happened not long after the Hatbox Ghost — long thought to be a rumor — was discovered to have actually been in the Mansion at one point, albeit briefly, and this, in turn, inspired Imaginnering to recreate Hatty and bring him back to the ride.
On the Long Forgotten blog (previously) we get a characteristically masterful analysis of Squeak, and all the ways in which she was exceptional: for one thing, she's the only one of Davis's cartoonish "bedsheet" ghosts that wasn't rendered in a more photorealistic style by Blaine Gibson in accordance with Walt's edict that the ghosts be "believable."
Which raises a couple of questions: why wasn't she placed in the Mansion? Here again, Long Forgotten has a very shrewd guess at an answer — after running down a few possibilities about why Squeak might not have made the cut, Long Forgotten offers a very compelling explanation. To get the joke that this maid is adding squeaks to a door-hinge, you'd have to be on a vehicle that was stopped long enough for the gag to be comprehensible, and that would be a hell of a long time.
There is another SDG mystery that is, to me, much more inexplicable. How did it get this far in development, even to the point of possible inclusion in the Orlando Mansion if Merritt is right, when it should have been obvious to everyone that the gag simply cannot be read in an instant, as all HM gags must be if they are to work. Davis explained the joke as a maid ghost trying to put the squeak INTO the hinges, transparently stepping back and forth through the door in the process. The latter element would require a Pepper's Ghost effect, but I imagine that part of it could probably have been sacrificed.
No, the real problem is that the joke would require several seconds of viewing, with a squeaking noise coming and going at appropriate intervals along with some way of signaling to the viewer exactly when the maid was applying oil and when not, so as to make it clear that the noise was being added to the door rather than eliminated. I'm surprised this concept made it off the drawing board.
Squeaky, we hardly knew ye.
The Squeaky Door Ghost [Long Forgotten]