Very Long-Forgotten Indeed
I'm going to call this character "Webster" for short, and "Web" for shorter. Web is a bona fide Mansion mystery, far more obscure than his Disneyland twin, the Hatbox Ghost. Here's the skinny: Webster either was or was not in the WDW Mansion when it opened. If he was, he was quickly removed, leaving behind no photos, and if he was not, he almost was. Sources disagree over whether he was ever seen by guests, or even whether he was installed. Some say he was canceled (or removed) because he was too scary. That description, down to the last detail, could have been applied to the Disneyland Hatbox Ghost prior to 1999. That was when Imagineer Chris Merritt published archived photos of the HBG in The "E" Ticket magazine. Unlike Webster, however, the HBG had never been completely forgotten, since he appeared in the narrative and artwork for souvenir record albums and in prototype photos used by Disney for publicity purposes. Nowadays, we even have film footage proving once and for all that the HBG was in the ride for a brief time. But Webster has never enjoyed any such luck and remains today an enigmatic figure.
Since the WDW Mansion opened in 1971, there have been only two significant discoveries about Webster. First, it was long-rumored that a piece of concept art by X Atencio existed, but the sketch was not published until 2009. You'll find it in the second edition of Jason Surrell's The Haunted Mansion: From the Magic Kingdom to the Movies. Thank you, Jason.
Coming out of that speaker below were the kinds of noises spiders make.