A spell gone wrong in a duel. A slip of a hand, A mispronounced word. Something goes wrong, and suddenly you get enveloped in a cloud of multi coloured haze. Everyone is frozen in panic, and when you emerge coughing from the cloud—everyone is still with shock. Y/n is transformed into a snake and emerges from his clothes on the floor. Macgonagall approaches and she is without appeal: the spell will last three weeks and Y/n will become human again at random moments for indefinite periods.