Professor Flitwick - "A lovely little thinker, but a bugger when he's pissed."

Snape gave Sprout a bucket filled with a foul-reeking potion. "Soak the bandages well in the mixture," he said, "that should heal the branches"
"Don't beat around the bush!" Sprout yelled. "Tell me what happened yesterday." "Filius challenged the Whomping Willow to a duel," he said.
Sprout looked furious. "And what, Severus, could bring Filius to do such a stupid thing? He usually prefers human opponents." "I don't know …" "He's been playing drinking games again, hasn't he? It's no secret Minerva can stick it away - half a crate of firewhiskey every day. I don't get why people are still trying to drink her under the table ." "You know how Filius is: a lovely little thinker, but a bugger when he's pissed!" Snape said with a smug expression on his face.
Sprout rolled her eyes. "Oh, honestly! Don't act as if you don't have anything to do with this mess, you silly drunken fart!" "But I haven't!" Snape's face turned brick red.
"Could you explain me then what your underpants are doing in the branches of the Whomping Willow?"