Catching him is easy. Keeping him is the problem.
Today the leprechaun is shorthand for luck. The older stories remember someone sharper.
In the National Folklore Collection at UCD, he turns up again and again as a solitary fairy shoemaker with gold hidden somewhere nearby. And again and again, the same rule: whoever catches him must keep watching. Look away for a moment, and he's gone.
An account from County Sligo describes the fairy shoemaker trying to make his captor look away. Another, from County Roscommon, tells it differently but ends the same way: the treasure is right there, and he is impossible to hold onto long enough to reach it.
Not lucky. Clever.
The figure in these stories isn't powerful. He's private, patient and always one step ahead. The real contest is not for the gold. It's for attention.
That older character is the one sitting on the pot of coins in Keeper of Secrets: not a mascot for good fortune, but someone who understands its value better than the person trying to take it.

He let you think you'd caught him.
How he was made → · The Leprechaun →
Further reading: National Folklore Collection, UCD, The Leipreachán and the Mermaid and Folklore.