Forcing the leprechauns to keep their Word and grant him any fairy wish, even a remarkably GREEDY wish is NOT the same thing as stealing their gold. As Goldy said in "Ducky Mt. High", " A deal is a deal". Mr. McDuck earned that wish by saving What's his name's life. And excuse me for saying so, but being remarkably GREEDY is VERY much in Mr. McDuck's nature.