In The Super Mario Bros. Super Show! episode "Mighty McMario and the Pot of Gold", Murphy's gold coins are stolen by King O'Koopa, and without his gold coins, the leprechaun becomes a jinx, bringing bad luck instead of good.
Murphy means well, as he treats Mario, Luigi, Toad and Princess Toadstool to lunch at the Shamrock Inn. However, his bad luck causes Mario to lose his lunch. On top of that, when King O'Koopa orders his Koopa Troopas to raid the inn, Murphy's bad luck causes Mario's group to get hurt.
After escaping from the Koopas, Murphy's bad luck eventually triggers a rain storm, which slowly starts to flood the Shamrock Kingdom. Mario and his friends try to get the Pot of Gold Coins back from King O'Koopa without Murphy's help, but when take took too long, Murphy goes after them, and his bad luck causes all of them to get caught.
Although Mario manages to find a way out of the dungeon, he tells Murphy to keep safe while he rescues Princess Toadstool. Unfortunately, King O'Koopa catches him, along with everyone else. King O'Koopa is proud of his accomplishments in the Shamrock Kingdom, and is ready to leave the place as it begins to start flooding.
When Murphy pointed out that his bad luck has ruined everything, Mario realizes that they had to use the bad luck to their advantage; namely, have Murphy act as King O'Koopa's best friend. When Murphy's bad luck rubs off on King O'Koopa, a series of mishaps cause him to blow up his own castle. Now afraid of what the leprechaun's bad luck could do to him, King O'Koopa surrenders, and falls into the moat.
Murphy then gets his coins back, and the curse is immediately broken. The rain storm stops, and a rainbow appears in the sky. Murphy gives Mario a hug, and he is relieved when nothing bad happened. Mario then falls through the floor, but realizes that it was good luck this time, for he landed at a table where a meal is waiting for him.