It's St. Patrick's Day at Ella Mentry School, and A.J. and the gang are celebrating, complete with a storytime about the legend of St. Patrick and cafeteria food that is all green. But as the kids research how exactly St. Patrick drove the snakes out of Ireland (and Andrea tries to convince everyone that snakes were never in Ireland), Mrs. Patty comes in with a snake of her own, which gets loose causing chaos everywhere. In the midst of all of this, A.J. is sure he spies a leprechaun, who plays tricks on the students of Ella Mentry. With all the pandemonium, can A.J. and his friends catch the mischievous leprechaun and find the runaway snake?