She was afraid you'd freak out? Start seeing demons in the White House? - Cassandra Clare

"Demon pox, oh demon pox
Just how is it acquired?
One must go down to the bad part of town
Until one is very tired.
Demon pox, oh demon pox, I had it all along — Not the pox, you foolish blocks,
I mean this very song — For I was right, and you were wrong!"

"Will!" Charlotte shouted over the noise, "Have you LOST YOUR MIND? CEASE THAT INFERNAL RACKET! Jem — "
Jem, rising to his feet, clapped his hands over Will's mouth. "Do you promise to be quiet?" he hissed into his friend's ear.
Will nodded, blue eyes blazing. Tessa was staring at him in amazement; they all were. She had seen Will many things — amused, bitter, condescending, angry, pitying — but never giddy before.
Jem let him go. "All right, then."
Will slid to the floor, his back against the armchair, and threw up his arms. "A demon pox on all your houses!" he announced, and yawned.
"Oh, God, weeks of pox jokes," said Jem. "We're in for it now."

Even in half demon hunter clothes, Clary thought, he looked like the kind of boy who'd come over your house to pick you up for a date and be polite to your parents and nice to your pets.
Jace on the other hand, looked like the kind of boy who'd come over your house and burn it down just for kicks.

What?" Simon looked alarmed. "I'm not really sleeping with your mom, you know. I was just trying to get your attention. Not that your mom isn't a very attractive woman, for her age.