Underpants of Doom.
I do not own the mortal instruments characters in any way, shape or form, I only own this plot and the hello kitty boxers. (Yes, I do actually have some.)
This is my first one-shot. I don't even know if this is a oneshot!

*BZZT* The sound of the dryer shutting off buzzed through the institute. Magnus Bane was sprawled in an armchair, idly reading a book while he was waiting for the laundry to be done. Since he had come to live in the institute, he was told by Maryse Lightwood that he had to help with the chores. And after a few holes in Jace's clothing, Maryse specifyed that the laundry must be done without magic. Alec readily agreed when Mayrse stated this during dinner, he was starting to be made uncomfortable, even though he didn't like Jace anymore, the holes were always in compromising places. Magnus agreed. *BZZT!* The dryer buzzed again, louder this time. Magnus sighed and stood gracefully from the chair. Walking towards the laundry room.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Magnus piled all the clothes on a spare bed to sort them by person. He threw one of Isabelle's shirts into her pile and grabbed a random clothing article. He lifted it up to see what it was,
"Ack!" Magnus choked. He was holding a pair of bright white and blue striped hello kitty underwear. 'They must be Isabelle's' He thought. "ISABELLE!" He yelled as loud as he could, a few seconds later she came running in. "What? What? Is something wrong?" She panted, looking frantically around the room for held up the underwear.
"Are these yours?" He asked calmly. She grabbed them and held them up to her waist, they were at least 2 inches too big.
"Do these look like they fit me? They're not mine! Maybe Clary..." She said. They looked at each other and at the same time yelled,
"CLARY!" 72 seconds later Clary walked in,
"Yes?" She asked. Magnus held up the ginch.
"These yours?" He questioned.
"No!" She looked at him incredulosly (A/N Spelling?), "I don't wear guy underwear." She stated.
"Wouldn't it be funny if it were Alec's?" Isabelle snorted, then paused. "Wait, it might be!" They all shouted at the same time.
"ALEC!" He sauntered in, looking melencholy, his expression brightened when he saw Magnus.
"Yes?" He asked, smiling. Isabelle grabbed the underthingies from Magnus and practically shoved them in his face.
"Are these yours?" She asked. Alec pushed them out of his face.
"Um... no! I would never wear this!"
"Alec, don't lie to your sister, I've seen your heart undies." Magnus stated calmly. Isabelle shrieked,
"What?"
"I know! I mean, typically, red and pink clash horribly, but it is somehow acceptable on valentine's da-" Magnus was interrupted.
"I'm not talking about his color coodernation! I'm talking about you seeing him in his underwear!"
"Look Izzy, Guy's. Sleep. In. Their. Underwear." Alec rolled his eyes at his sister's dramatic tendencies. Magnus decided to change the subject before it got any more awkward.
"So if they're not any of ours... that only leaves... Jace?" Suddenly, Jace walked in, he took one look at the underwear in Magnus's hand and grabbed them.
"Why do you have my underwear?" He said questioningly. Everyone just stared in shock as he left the room, then laughed uncontrollably until their faces were red.

Alright, I know that was terrible, but I was bored. And wanted to write. A dangerous combination. Oh well.