I haven't heard anything about this at WDW but that doesn't mean it doesn't exist.
It does sound similar to something done at DLR in the past. I believe it was done in conjunction with the annual re-theming to the Nightmare overlay.
Maybe someone else knows more.
And lots of expensive trinkets ( I own a few of those from 999 ) -- my understanding is they are not having it this year.......when I checked with the Art of Disney @ EPCOT and talked to some very reliable CM's -- I wanted to place my order for things like theHarmony Kingdom piece, I was told the event probably wouldn;t take place in 2005...but they really weren't told why
Oh Yeah, and somewhere in the evening you got a drive by from the Headless horseman - which is pretty cool
" Disney Parks- far from perfect- but still a great shelter from the storm "