The Jumpity-Jim appears in a short story written by author R. Chetwynd-Hayes in one of his short story collections entitled The Elemental (Fontana 1974).
The Jumpity-Jim is described as looking like a cross between a deformed monkey, and a monstrous spider. The face is deflated, and the body is long and an unnatural pink in color. It garners its name from its ability to leap about with prodigious speed and agility. The Jumpity-Jim is described within the story as being an Elemental, though it acts more like an ectoparasite. The incantation for summoning the monster can be found in the fictional book by Conrad Von Holsteinentitled Unnatural Enmities And Their Disposal, from which the following excerpt is taken:
"The Primate Horrific or Jumpity-Jim hath little intelligence, being but a form of low existence that doth demand life essence and warm blood. Once it hath been raised it will leap about with much speed and agility, and, if that which it needs be not at hand, will depart with a mighty explosion.
But should there be within the radius of twenty feet, a virgin, who hath the right essence, and should the flesh of her back, that which lies between the neck and the upper portion of the loins, be bare, then will it leap thereon, and will become as part of the poor wretch, as doth the legs and other members that did God in his bountiful goodness provide.
Once the abomination has mounted the steed, it can in no wise be removed, unless a like-virgin, cursed with the same essence, can be induced, or forced, to accept the loathsome burden."
There seems to be absolutely nothing gained from summoning a Jumpity-Jim. It does not imbue the victim with super strength, immortal beauty, or any other worthwhile augmentation other than a large hump positioned between ones shoulder blades. Once the monster is taken from the nether-world it can never return, for it has taken on the flesh of a meat eater. The only way for it to survive is to move from host to host for eternity.
No earthly walls can hold a Jumpity-Jim.