The Elastic Ghosties are a duo of ghosts (or possibly some other sort of spirits).
Mysterious and not a little scary, these small wispy spooks are among the residents of Disneyland's Haunted Mansion, though they are not seen on regular tours. White or green, they have strange ability to make their head float away from their bodies.
Behind the scenes
The Ghosties, sketched in Haunted Mansion concept art by Marc Davis then forgotten, were featured in the illustrations of The Story and Song from the Haunted Mansion (though they have no role in the audioplay) and one of them can also be seen in Magic from the Haunted Mansion.
The Ghosties are in the same conceptual range as the Organ Banshees, design-wise, especially as the Banshees appeared to be floating wisps not particularly related to the organ in the earliest concept art where they appear.