"I'm not sure if you've noticed, Ron," said Hermoine over cocktails, "but Harry's been making a funny ticking noise."
Ron laughed, an empty hollow laugh that rang around the stone bar/corridor and sent smaller children scattering for cover. "Better go and check it out, then!"
They crept up the stairs of Harry's tower (he'd been giving it after doing rather well at Quidditch) and peeked through the door. What they saw on that fateful day gave them the fright of their lives.
Harry stood at his full length mirror. He raised his hands to his head – and pulled it right off his shoulders! Wires spilled out of his neck.
"Crikey, Harry's a robot!" exclaimed Ron. "Quick, scarper!"
And so they did.