The Thing is a monster (possibly only comprising a hairy disembodied hand).
The Thing was only ever observed as a hairy, monstrous hand which may not actually be attached to any kind of a body. Seen poking out of a coffin-shaped refrigerator set in the wall of the Haunted Mansion kitchen, it helpfully passed ingredients to a group of witches led by Phyllis Diller as they brewed a potion.
Behind the scenesEdit
It is, of course, a thinly-veiled cameo of the Thing as it appears in the Addams Family franchise, the only significant difference being that the original Thing resembles a regular human hand, not a hairy monster one. As such, the Thing is also, to some extent, a remembrance of Hairy the Arm, a deleted monster from early in the Haunted Mansion’s development. The catchphrase uttered by Addams Family characters whenever the Thing acts helpfully to them is "Thank you, thing", willfully misquoted in the Disney film as "Thanks, Thing" by Phyllis.