According to Irish legend, or folklore, Leprechauns have a hidden pot of gold. If you catch a Leprechaun, he must give you his pot of gold.
Leprechaun
A leprechaun (Irish: leipreachán) is a type of fairy in Irish folklore, usually taking the form of an old man, clad in a red or green coat, who enjoys partaking in mischief. Like other fairy creatures, leprechauns have been linked to the Tuatha Dé Danann of Irish mythology.
The Leprechauns spend all their time busily making shoes, and store away all their coins in a hidden pot of gold at the end of the rainbow. If ever captured by a human, the Leprechaun has the magical power to grant three wishes in exchange for their release. Popular depiction shows the Leprechaun as being no taller than a small child, with a beard and hat, although they may originally have been perceived as the tallest of the mound-dwellers (the Tuatha Dé Danann). The leprechaun originally had a different appearance depending on where in Ireland he was found.