Cloud of Chaos - S1.E20

Sproggle is accidentally thrown from the Paradox and falls through a blue cloud during a close encounter with Dr. Agon's Mammoth Machine. The villain ‘rescues' the orphan but once they are both aboard the Mammoth Machine, both are oddly affected by the cloud and swap personalities. Dr. Agon becomes Sproggle while Sproggle turns into Dr. Agon!