I think he's jealous.

Magnus glanced at Alec and raised his eyebrows "Boo", he said. Jace was grinning. "Come on,surely you've got a phobia or two. What scares you?" Alec thought for a moment. "Spiders," he said. Clary turned to Luke. "Have you got a spider anywhere?" Luke looked exasperated. "Why would I have a spider? Do I look like someone who would collect them?" No offense," Jace said, "but you kind of do.

And in some way, Clary thought, he meant it, meant his gratitude. He had long ago lost the ability to distinguish between force and cooperation, between fear and willingness, between love and torture. And with that realization came a rush of numbness—what was the point of hating Valentine for being a monster when he didn’t even know he was one?

Anything?" She laughed. "Like what kind of anything did you want?" "Well, when I was five, I wanted to take a bath in spaghetti." -Clary & Jace, pg.310-

But the person who stepped out of the front door was tall and thin, with short, spiky dark hair. he was wearing a gold mesh vest and a pair of silk pajama pants. He regarded Clary with mild interest, puffing gently on a fantastically large pipe as he did so. Though he looked nothing at all like a Viking, he was instantly and totally familiar. Magnus Bane

Wear that scarf," he said, pointing to a blue cashmere scarf hanging on a peg. "It matches your eyes." Alec looked at it. Suddenly he was filled with hate - for the scarf, for Magnus, and most of all for himself. "Don't tell me," he said. "The scarf's a hundred years old, and it was given to you by Queen Victoria right before she died, for special services to the Crown or something." Magnus sat up. "What's gotten into you?" Alec stared at him. "Am I the newest thing in this apartment?" "I think that honor goes to Chairman Meow. He's only two." "I said newest, not youngest," Alec snapped.

Jem shook his head. "You bit de Quincey" he said. "You fool. He's a VAMPIRE" "I had no choice" said Will " He was choking me" "I know" Jem said. " But really Will, AGAIN?