“Deliberately causing mayhem in Snape's Potions class was about as safe as poking a sleeping dragon in the eye.”

“Snape was looking as though the first person to ask him for a Love Potion would be force-fed poison.”

“I think I'd better do the actual stealing," Hermione continued in a matter-of-fact tone. "You two will be expelled if you get into anymore trouble, and I've got a clean record. So all of you need to do is cause enough mayhem to keep Snape busy for five minutes or so.”

“Never tickle a sleeping dragon.”

“Dumbledore watched her fly away, and as her silvery glow faded he turned back to Snape, and his eyes were full of tears."After all this time?""Always," said Snape.”

“This is your copy of Advanced Potion-Making, is it, Potter?”“Yes,” said Harry, still breathing hard.“You’re quite sure of that, are you, Potter?”“Yes,” said Harry, with a touch more defiance.“This is the copy of Advanced Potion-Making that you purchased from Flourish and Blotts?”“Yes,” said Harry firmly.“Then why,” asked Snape, “does it have the name ‘Roonil Wazlib’ written inside the front cover?”Harry’s heart missed a beat. “That’s my nickname,” he said.”

“Draco Dormiens Nunquam Titillandus[never tickle a sleeping dragon]”