Shoko

The Mansion Ghost appears in "The Creeps" when Finn is the last one 'alive' and hides in a room with multiple bookshelves. The Mansion Ghost appears, and Finn breaks through the wall to the next room. Everything in the episode was a prank, except for the Mansion Ghost, who Jake had no idea about when Finn asked him if he had set up that as well.

Appearance
The Mansion Ghost has light greyish-blue skin with long green seaweed-like hair. It is implied that she has the ability to make objects float, where as when she appeared multiple objects were floating around her in mid-air.