The Northern Irish Leprechaun resembles the traditional Irish Leprechaun, except he wears all orange to show his support for the Orangemen (Protestant Unionists). He looks like his counterpart except he has bushy eyebrows and mutton chop whiskers and wears a frock coat with tails, a white dress shirt with a bow-tie, and a top hat.
He is first shown leading the Protestant St. Patrick's Day Parade (in which the marchers wear orange clothing) in opposition to the Catholic St. Patrick's Day Parade (who wear green clothing). When Bart asks Lisa what they are fighting over, she sighs, "It always comes down to trans-substantiation versus con-substantiation."
Lisa tries to calm the mobs with an Irish lullaby, which moves them to hugging and crying. However, the Northern Irish Leprechaun is soon viciously battling it out with his Catholic counterpart after the Catholic Leprechaun sucker-punches him. During the ensuing melee, Marge comments, "This was such a pleasant St. Patrick's Day until all the Irish people showed up!"
He appears on the box for Belfast Charms
When the town is divided between whether or not the Simpsons should share the money they get from a painting they get from the Van Houtens, he is for the Simpsons to share the money.