S1, E26: The last field trip of the year is also the most important: the class must go to the center of the Sun to recharge the bus’s Magic Battery, the source of the bus’s magic. But when Mr. Ruhle, principal, safety nut, and amateur sun enthusiast, tags along, Arnold must preserve the secret of the field trips to prevent him from cancelling them altogether. But escalating mishaps, including launching Mr. Ruhle into space and the bus running out of reserve power, mean that Arnold must find the personal courage to save the bus, the class – and the magic!