They appear in the novels Carpe Jugulum, The Wee Free Men, A Hat Full of Sky, Wintersmith, I Shall Wear Midnight, Snuff, and The Shepherd's Crown.
In The Art of Discworld, Pratchett identifies The Little Grey Men and Down the Bright Stream, both by "BB", the nom-de-plume of Denys Watkins-Pitchford, as possible inspiration, featuring fairies that could talk to creatures, but "there was nothing tinkly about them; they lived in a world of dangers".
According to their own history, the Nac Mac Feegle rebelled against the wicked rule of the (or possibly "a") Queen of the Fairies, and were therefore exiled from Fairyland.
As the Big Man of the Chalk Hill Gang, Rob Anybody, proudly states: "We've been robbin' an' runnin' aroound on all kinds o' worrlds for a lang time."
Those who have actually witnessed "the crawstep" report that the Mac Feegles simply stick one leg straight out in front of them, wiggle their foot, and are suddenly gone.
One of the buzzards, Morag, owned by Officer Buggy Swires of the Ankh Morpork City Watch was trained by the Feegles, for the price of several crates of strong liquor.
The new kelda chooses her husband, known as the Big Man, from among her adopted Clan when she arrives, and soon begins the lifelong task of begetting the next generation, often up to one hundred tiny baby Feegles at a time.
Theoretically, (and on the Discworld theories of this nature tend to work, even if they are not actually right, owing to narrative causality), the bottle contains water from the cauldrons of Nac Mac Feegle keldas since before history.
When encountering a foe much larger than themselves, (which is most anything the Nac Mac Feegle pick a fight with,) the clan will stack themselves up like a pyramid, until the top one is high enough to punch the enemy or, preferably, head-butt them.
Among the warriors of each clan is a gonnagle; a bard or war-poet, whose job is to create terrible poetry that is recited during battles to demoralise the enemy, (see William McGonagall.)
In A Hat Full of Sky, the gonnagle, Awf'lly Wee Billy Bigchin, can play the mousepipes so sadly that it will start to rain outside.
The Chalk Hill Clan had, until the arrival of their new kelda Jeannie from Long Lake, a superstition that anything written down could be used against you in a court of law, and each of them carried swords that glowed blue in the presence of lawyers.
The Long Lake Clan have similar superstitions about writing and lawyers, but believe it's possible to beat them at their own game and are famed for their "verra com-plic-at-ed documents".
They comically fear witches who know about them, with large amounts of dread being reserved for "the Foldin' o' the Arms", "the Pursin' o' the Lips", and the "Tappin' o' the Feets", followed by "the Explainin".
They reason that Discworld, with the sunshine, flowers, birds, trees, things to steal and people to fight, must be some sort of heaven, because "a world that good couldn't be open to just anybody".
Thus, they do not mourn the loss of Mac Feegles who have died in battle on the Discworld, according to The Wee Free Men: "Oh, they've gone back to the land o' the livin'.
Indeed, any grieving a Feegle might do over fallen family members is never about their actual death, but rather over the fact that he did not get to spend more time with them before they rejoined the land of the living.
[4] The kelda in Wee Free Men states that "in our tongue you'd be Tir-far-thóinn"[3] (an alternative name for Tír na nÓg),[5] suggesting that in private their speech may be closer to Irish or Scottish Gaelic.
[6] In Carpe Jugulum, their speech is almost undecipherable and has to be translated by Nanny Ogg; however, by the time they meet Tiffany Aching, they are somewhat more understandable to "bigjobs".
Gnomes and the Nac Mac Feegle share a lot of the same characteristics, such as immense strength, bellicose personality and the use of tamed birds as lookouts.
In the Discworld Companion, Pratchett describes Wee Mad Arthur, an Ankh Morpork gnome, as an urbanised Nac Mac Feegle, (however, he is later revealed to be a Feegle (see above)) and Paul Kidby's illustration of Buggy Swires in The Art of Discworld is indistinguishable from the pictsies on the cover of The Wee Free Men.
Gnomes are also featured in the short story Theatre of Cruelty, in which a children's entertainer forces them to perform as a Punch and Judy show.
Eileen Donaldson, writing in The Gothic Fairy Tale in Young Adult Literature: Essays on Stories from Grimm to Gaiman, notes that Pratchett "satirizes our expectation of fairy-folk (wings, flowers, and "tinklyness") through the Feegles who curse, drink, fight, steal, cause chaos and are feared by everyone".