He he he... in a huge two-DM 2e campaign I once played (and DM'd) in, a paladin named Meriadoc (I, unfortunately, had never read LotR, thus didn't catch the name) came upon leprechans twice. Once was in the forest, in which the little guy stole all the paladin's gold and then tricked him into falling down a ditch.
The other leprechaun was named Bedlam, who held a Totem Deck (a less powerful, monster-themed Deck of Many Things). Meriadoc took a couple cards, and became a goat-headed paladin with slow cast on him and a turkey leg for a sword.
Least to say, Meriadoc never liked leprechauns...