Are there exactly 999 ghosts/ghost effects in the mansions?
No. There are well under 999 actual ghost figures and effects in the mansion. The 999 happy haunts/room for a thousand thing is just a cute way of playing up Walt Disney’s original “supernatural real estate” gag, conceived early in the planning stages of the project. In the 1950s, while visiting England, Walt publicly broke his plans for a haunted attraction in a BBC radio interview. He announced his intention to recruit old ghosts to come live and “perform” at Disneyland, claiming inspiration by all of the ancient ghosts displaced from old British homes during wartime and urban renewal. The “spooky retirement community” concept continued into the 1960s with Marty Sklar’s “real estate sign” copy (see above), and strongly influenced me in developing the “home and garden” spoof slant for this web site. If you’re serious about your numbers, WDI Senior Creative Veep Tony Baxter suggests including the wallpaper demons from the Corridor of Doors in your count.