"Banshee" comes from "Bean Sidhe", and translates as "Woman Fairy." The banshee appears only to certain Celtic families, Irish, Scotch, and I believe Breton and Welsh -- I am unaware of any similar tradition among the Cornish and Manx. Death portents such as the banshee also appear in other cultures. Usually the banshee is an old woman, but can be a young woman of exceptional beauty. There's a very comprehensive book on the banshee (called, believe it or not, "The Banshee"); I'd give you the author but I can't put my hands on my copy right now.

The leprechaun has a cousin, the clurican and I find the clurican the more interesting. If you have liquor around and the clurican shows up, your liquor will disappear. Some have called the clurican a leperchaun on a spree.

The shape-changing pookah has corollaries in many other cultures, including the Native American. A pookah bodes no good for anybody it appears to. There is a legend of a jewel-encrusted pookah inhabiting one of the lakes on the Castlegregory side of the Conar Pass.

The sidhe is a topic of wide-ranging interest. Just remember that the sidhe were NOT cute little people, a la Darby O'Gill, but were just a tall and just as cunning and brave as you or me -- not at all like in the poem:

Up the airy mountain,        
Down the rushy glen        
We daren't go a-hunting        
For fear of little men;        
Wee folk, good folk,              
Trooping all together;        
Green jacket, red cap,        
And white owl's feather!        
Down along the rocky shore        
Some make their home,              
They live on crispy pancakes        
Of yellow tide-foam;        
Some in the reeds        
Of the black mountain lake,        
With frogs for their watch-dogs,              
All night awake.        

High on the hill-top        
The old King sits;        
He is now so old and gray        
He's nigh lost his wits.              
With a bridge of white mist        
Columbkill he crosses,        
On his stately journeys        
From Slieveleague to Rosses;        
Or going up with music              
On cold starry nights,        
To sup with the Queen        
Of the gay Northern Lights.        

They stole little Bridget        
For seven years long;              
When she came down again        
Her friends were all gone.        
They took her lightly back,        
Between the night and morrow,        
They thought that she was fast asleep,              
But she was dead with sorrow.        
They have kept her ever since        
Deep within the lake,        
On a bed of flag-leaves,        
Watching till she wake.              

By the craggy hill-side,        
Through the mosses bare,        
They have planted thorn-trees        
For pleasure here and there.        
Is any man so daring              
As dig them up in spite,        
He shall find their sharpest thorns        
In his bed at night.        

Up the airy mountain,        
Down the rushy glen,              
We daren't go a-hunting        
For fear of little men;        
Wee folk, good folk,        
Trooping all together;        
Green jacket, red cap,              
And white owl's feather.