McGonagall cleared her throat suddenly. "Oh Mr Potter, before you go and give your lecture ..." She glanced at him, her lips twitching. "Do brush your knees."

I was so relieved for Harry and Draco until McGonagall said this. I wish I could have seen their faces. *sighs* I bet it was priceless.
Anyway, this was a great story. I loved every sentence =]