Luck O' The Chipmunks is episode 70B in Season 6 (1988) of The Chipmunks.
While Simon and Theodore are performing a demonstration about why scientists can't turn lead into gold, Micky, a new Irish student, arrives in class only to be laughed at when his magic trick doesn't work as planned. When Theodore's new-found friendship with Micky is threatened by his brothers, Micky claims that he has his very own leprechaun that only appears at sundown. Once Alvin finds out, he is determined to find out whether the claim is true. When the leprechaun (which is really Micky) grants their wishes (a new tire for Alvin and Simon's experiment to work), Alvin undergoes a scheme to make money from him. After granting long lists of wishes, Micky is tired. Simon reads that after a leprechaun is caught they must grant three wishes and give the captor a pot of gold. The boys soon discover Micky is really the leprechaun after he falls into the river and had only created the lie to make friends.