Mr. Green (Powerpuffs Toons)

Appearance and Personality: He has green skin, long white hair, gray ram-like horns, and an eye patch. He wears a long cape and dresses like a fairytale villain. Despite his frightening appearance, he is a very kind teacher who loves teaching children. He occasionally brings them cookies.
Mr. Green initially makes a dark and unsettling entrance, but then becomes polite and calm. He announces that he will be the substitute teacher for the class that day, as Mrs. Keane is ill. (Because of his monstrous appearance.)
Occasionally, he can lose control when he becomes overwhelmed by the stress of caring for children, which rarely happens. However, if someone is injured and the smell of their blood or nervousness reaches his nose, he can slowly lose control, experiencing a coughing fit and becoming nervous and panicked at the thought of harming his children. That's why he needs to take a few moments outside to regain his composure. In more extreme cases, if it's already too late, he must lock himself away until his true transformation into a terrifying creature takes over. This is his alter ego, the one that eats children. Its symptoms manifest as mild coughing fits, forcing him to close his throat and contain his evil madness with muffled groans.