Glorpy has become a sort of badge for magicians (including illusionist's) over the years in my opinion, just like the coin manipulator will walk a coin across his knuckles, Glorpy has sort of filled that role at Halloween. Glorpy makes a perfect break from the spookier magic, its a quick eye catcher, and Glorpy is very intimate, usually one on one and table hopping.
The pro's for this effect go on and one, nothing added or taken away, always ready, no reset (unless you consider folding the hank a reset), angle proof, fits in your pocket, and inexpensive at under $10. As already said the effect is great for breaks and impromptu gatherings, but it also can be used to enhance other effects... Example - Put it on top of a set of spirit slates and watch the spooks write with the chalk.
If there is a con for this effect its that it could be interpreted as a poor man's dancing hank. Also this is priced at a level every ten year old could afford with his allowance (What saves this from complete exposure is the real work is the presentation and even if someone in your audience owns this effect, if you perform it well they will not even recognize it). Perhaps its biggest con is most magician's look at the price and don't give the effect a chance, not wanting to risk their good reputation on a $7 prop.
The effect takes a little practice to get familiar with it, and its almost all presentation so the better you can present yourself and this effect, the better the effect will be perceived by the audience.
The performer displays a handkerchief, lays it on a table and folds it over into a square. He catches a ghost called Glorpy, lifts one corner of the square, and tosses him into the handkerchief. For the skeptic who doesn't believe in ghosts, the magician offers to prove that Glorpy really exists.
Glorpy now begins to gerkulate as the center of the handkerchief rises and falls uncannily. Finally on command from the performer, Glorpy stops gerkulating, disappears and the handkerchief is shown free of any attachments, folded up and placed in the pocket.
This is the ORIGINAL and BEST haunted handkerchief effect. Do not be fooled by imitations!