Everyone should have received a modest update to the game files today. As many have speculated, it was to prepare for a special prize to be awarded tomorrow, on Halloween. As long as you log in to your game between 7am Oct 31st GMT and 7am Nov 1st GMT, you will get the characters’ dialog and have the item placed in your inventory.
What’s the special item? There was speculation it would be a new decoration called the Devil’s Anvil, whose graphic had appeared in the files. But either it wasn’t ready, or they wanted to give us something that would produce more ghosts and GOO.
So, the answer is a Wailing Wall! Not bad, it normally costs 50 donuts, produces 6 ghosts every 12 hours, and provides a nice 2.25% bonus to XP and $. It can be placed on grass, pavement, or the beach. Presumably after the Halloween event ends, it will generate $ and XP every 12 hours.