I'm Draco Malfoy, I'm Draco, I'm on your side!"
Draco was on the upper landing, pleading with another masked Death Eater. Harry Stunned the Death Eater as they passed: Malfoy looked around, beaming, for his savior, and Ron punched him from under the cloak. Malfoy fell backward on top of the Death Eater, his mouth bleeding, utterly bemused.
"And that's the second time we've saved your life tonight, you two-faced bastard!" Ron yelled.”
FROM:
Harry Potter and the Deathly Hallows

“Honestly, if you were any slower, you’d be going backward.”
FROM:
Harry Potter and the Chamber of Secrets

“Longbottom, if brains were gold, you'd be poorer than Weasley, and that's saying something.”
FROM:
Harry Potter and the Philosopher's Stone