You suddenly notice the maths teacher is wearing a small blond wig, crowning his bare scalp and the darker hair around it. You wonder for a moment when exactly he ha the time to put on that ridiculous hairpiece, when you see the blond hairs twitching... no, growing!
You look around the classroom and sure enough, everyone else notices it too. Your maths teacher is growing a new head of hair before your very eyes!
You realise the teacher's voice is several octaves higher now, when did that happen? It must've happened gradually, a transition from gravelly middle-aged man to a cooing, breathy (and distinctly feminine) voice so slow as to be unnoticeable from one minute to the next - but it was really obvious to you now.
To hear that sultry voice leave the face of that man was a surreal experience, as his newly-found thick, blond locks fall down the sides of his face in shimmering curls and show little signs of stopping yet...