Leprechaun (monster class)
The leprechaun is among the many monsters present in the very first version of Hack by Andries Brouwer, along with "Hack for PDP-11" (which was based on an early draft). In early versions such as this and NetHack 1.3d, leprechuans used the L glyph and had slightly different behavior: they would still attack players that closed in as they attempted to keep their distance.
Some variants opt to further populate the leprechaun monster class so that it has more than one member. In addition, variants featuring an object materials system commonly give members of the leprechaun monster class the ability to steal gold items.
SLASH'EM introduces the leprechaun wizard, which has slightly better AC and the added ability to cast clerical monster spells. While leprechaun wizards do not spawn in leprechaun halls, leprechauns can grow up into leprechaun wizards - a leprechaun generated with a potion of gain level can quickly become an item-cursing annoyance. Both monsters can also hit as a +1 weapon.
SlashTHEM has several new monsters in the leprechaun class. Almost all of them have teleportitis and a gold theft attack - the sole exception is the pooka, which lacks any gold-stealing abilities but still has an item theft attack.
xNetHack version 3.0 merged leprechauns into the i imp or minor demon class, with xNetHack changing the glyph for the lizard monster class to lowercase l (l) instead to avoid using a punctuation glyph. However, this is reverted as of version 6.0.