Leprechauns where Demonic spirits of sorts in Celtic mythology.. kinda like.. a poltrighist (bad spelling) is to us.. a spirit that messes with you..
which can give you good luck, or terrible luck.
Also, from readings on mythology.. I have never read anywhere that Leprechauns where actually short at all.. nor where they Green.
(Well I take that back, plenty of accounts of little Leprachauns, but it seems the older the story the less a Leprechaun is like modern Leprachauns ..
and I do find it unusual that we still put them in a 1600's pilgrims costume..)
[edit on 3/17/2008 by Rockpuck]