With magic leprechaun powder. You have to sprinkle it on their forehead.
There is no knowledge it is said, that is not power. It is our knowledge and know-how of leprechauns that can help one catch a leprechaun. It is well known that leprechauns dress in green coats with green hats and that they wear green hats. It is also known that they like to drink and that they are greedy. Their profession is believed to be repairing shoes. All these items can thus be used as bait. For instance a bright green coat, or a decorated hat, an old shoe, a few pennies, fake gold coins, a jar of ale etc can thus all be used as bait in laying a trap for the leprechaun. A well masked cage can be used with a snap shut door can be used. Be careful once the little devil is caught as they are masters at escaping from tight situations.
that's impossible .
Look I know you try to catch leprechauns and they are real so find a 7 leaf clover and look beside it and keep looking till you find a leprechaun then catch it then hold it till you get a pot of gold.