If you do a web search for "Hsigo", you will find thousands of references and hundreds of images. I won't give specific references, because they're all complete and utter nonsense, but you can read detailed descriptions of these fake, mythical Chinese monkeys — including pseudo-learned discussions of their name — in works like the following: Erudite Tales, Creepy Hollows Encyclopedia, Mythical Creatures Guide, Encyclo, Societas Magic, Monstropedia, etc., etc. Hsigo are supposedly flying monkeys with bird-like wings, the tail of a dog, and a human face.
There's even a very brief Wikipedia entry for Hsigo, but I know a top Wikipedia editor who is endeavoring to liquidate that totally fictitious article as a first-step toward eliminating "Hsigo" lore from the Web and hopefully from circulation elsewhere as well.
It all started with a typo. See "'Hsigo', the viral OCR typo". This detective article is really quite entertaining and edifying. It ends with a reference to what our Language Log colleague, Geoffrey Nunberg, calls "the 'metadata train wreck' of Google Books".
If you want to see how such false entries begin and how hard it is to weed them out, read through the documentation below. I have been given permission to quote from Talk:Hsigo; WP is all CC-BY-SA 3.0 Unported License.
The Revision history is interesting (you can click through the links and check differences).
An anonymous IP (220.127.116.11, clicking "Geolocate" at bottom shows Bremerton WA) started the article on 1 January 2005
"RandyS0725" added the only ref on 23 December 2012
Here are some statistics (only a dozen page views per day).
Besides the giggles provided by Googling for "hsigo", the more serious question becomes: how many other OCR ghost-words exist in the metadata? My friend randomly came across this page and only saw the mistake because he has studied Chinese transcription systems and monkey mythology. If he had not caught it at this already somewhat advanced stage, who knows how deeply the Hsigo would have become embedded in human consciousness.