Author's note: Decided to do a few Halloween-themed stories and this was the first that came with help from the bestie writingbutunpublished. I posted it in three parts on my tumblr booksrockmyface, but decided to put it all together here for your enjoyment. Please let me know what you think.

Happy reading!

"I'm a Mouse, Duh."

A TMI Fic

Clary and Simon had been whispering in corners for days. Jace and Izzy watched them in concern, but they never said anything when asked what was up. So they mostly left the friends alone.

Clary said, "We need to just ask him already. You know we can't do anything here."

"And he does throw some amazing parties." Simon countered.

"So, let's go." Clary stood and sent off a text. She found Jace in the weapons room with Izzy.

"You're sharpening that too much." Jace commented.

"You're hovering." She shot back.

"You're both pretty." Clary said.

They looked up.

"Magnus just sent me a text to hang out." She waved her phone. "Wanna go?"

"Sure." Jace and Izzy said at the same time.

It had been a while since they had seen their brother and they welcomed any chance to see him outside of patrol.

They gathered their things and were out the door in just a few minutes. They arrived at Magnus's apartment in good time, traffic wasn't too horrible.

"What is the meaning of this?" Magnus asked, holding up his phone.

"Well, hello to you, too." Simon quipped.

"A costume party?" Magnus asked. "In two days?"

"You know you can throw it together." Clary encouraged. She plopped down on the couch beside Simon. They both leaned forward.

Simon added, "Come on, Magnus."

He sighed dramatically. "I suppose we could do something."

Alec shook his head. "I don't think I like this."

"You will when you see what I could put you in."

"I'm sure something where I'm wearing little-to-nothing." The Shadowhunter grumbled.

Izzy, who had been sitting with her arms crossed, not liking the idea of the costume party idea, perked up. "Wait, what exactly would we wear to this thing?"

Simon wrapped an arm around her shoulders. "You could put on one of your tightest outfits get yourself a pair of pointed cat ears. Boom, you're a cat. A very, very sexy cat."

"I still think this is ridiculous." Jace said. "I am not wearing anything abnormal."

"You don't have to wear anything abnormal." Clary assured him.

"You would somehow force me to." He argued.

She leaned in and whispered, "And when was the last time I ever forced you to do anything you didn't want to?"

"I could name a time or two." He said. "But not in current company."

She grinned. "Current company aside, my darling, let me just say, you are perfectly fine the way you are. You don't have to do much at all. You're already a superhot Shadowhunter. Just go as yourself."

"Nope, that's one of the rules! Can't be yourself." Magnus countered.

"Just wear tightest clothes and add some cat ears." Alec suggested with a wink.

"You would like that, wouldn't you?" Jace teased.

"Oh, you know it." Alec chuckled.

"I know!" Izzy said. "There is some old gear in the attic from about a hundred years ago. It's still in very good condition. We can fix anything that is in disrepair."

"You could even darken your hair and say you're William Herondale." Magnus suggested.

This earned a glare from Alec.

"Turn off the jealousy, Alexander, I was never in love with William Herondale. For the millionth time."

"That could be fun." Clary said. She gave her boyfriend an imploring look. "Please, Jace?"

He sighed and looked around the room. "Okay, I guess I can do that."

Clary and Simon shared a high-five.

"Okay, so where do we start?" Clary asked enthusiastically.

For the rest of the afternoon, Clary, Simon, and Magnus planned the party. The other three sat in a circle off to the side and watched in fascination.

Clary stood in front of a mirror. She wore a blue sleeveless shirt and baggy gray pants. She had her hair pulled up in a high ponytail wrapped in blue cord. She sat down and pulled on some cloth-lined boots.

"And you're supposed to be…?" Jace said as he watched from the doorway.

"Korra." She smiled and stood. She executed a turn. "What do you think?"

"I think that I don't understand at all who you are. But you look cute."

"I wasn't looking for cute, I was going for fierce." She pulled warmers on her wrists and picked up a blue and white band and passed it to him. "Will you help me with this one? It goes here." She pointed to her right upper arm.

After he strapped it on he stepped back. "So what does this Korra do?"

"She bends elements." Clary said with a grin. "She comes from a water tribe…" She trailed off and shook her head. "Never mind. I won't bore you with all the details. Let me get a good look at you." She stepped back and crossed her arms.

He wore an old-fashioned black shirt tucked into a pair of black leather pants that formed perfectly to his muscular legs. He wore a long coat that stopped at his calves. It fastened in the front with large ornate buttons. He wore his own boots. "What do you think? Am I a proper Victorian Shadowhunter?"

Clary nodded appreciatively. "You look great."

"I'm even wearing a Victorian breastplate underneath." He tapped on his chest. "I look fashionable and I can fight any demon should they cross our path or get out of hand."

She chuckled. "I like that."

"We should do some role-playing when we get back from the party." He whispered.

She giggled. "My mom is expecting me to come home after the party and be home for a while."

He sighed. "Well, I know a trick or two to get into your house without your parents knowing."

"My parents are both former Shadowhunters and my dad is a werewolf. Do you really want to risk it?"

"I don't guess so." He held out his hand. "Come on. Simon and Izzy are waiting."

Thanks to the encouragement of her boyfriend, Izzy was wearing a tight black dress that stopped mid-thigh, knee-high black boots and a pair of cat ears tucked in her flowing dark locks. She'd gone so far as to bring her eyeliner out to a point on either side of her eye. She wore bright red lipstick. That was the extent of her costume.

On the other side of the spectrum, Simon was wearing a white shirt under a brightly patterned vest, gray trousers, a long brown coat, and topped off with a very long scarf made of many different colors of yarn wrapped several times around his neck.

"You both look so fantastic!" Clary gushed.

"Who are you supposed to be?" Jace pointed at Simon.

"The Fourth Doctor." Simon said confidently.

"Don't doctors wear white coats?" Jace was so confused. "And why the Fourth specifically? Is that a type of doctor? What do you heal?"

Izzy placed a hand on his arm. "It's some television show. Don't question it. It's far too confusing."

"It's about a guy who travels through space and time." Clary explained. "Not too confusing."

"It is confusing." Izzy said. "There was something about a tortoise and a man that regenerates. And there are… companions?"

"TARDIS." Simon corrected. "We'll watch it sometime."

"But we haven't finished all of Xena yet." Izzy argued.

"There's plenty of time." He assured her as they made their way outside.

"Hello, Doctor." Magnus grinned when he greeted them all at the door. "The rest of you look great, but I think Simon wins."

"I worked really hard on this." Jace whined.

"You'll somehow survive not being the one best dressed." Clary informed him. "You are still the most attractive in the room to me."

"Aw, how sweet." Izzy said.

"Gag." Simon said.

"Come on." Izzy said, pulling on Simon's arm. "Let's mingle."

"And you are a gladiator?" Clary asked as she looked over Magnus's brass chest armor and leather skirt.

"One of the Sacred Band of Thebes. Alec and I are a matching set." He grinned. "He wears it better being a fighter already and all."

"I definitely have better legs for it." Alec grinned as he sauntered over. "You look really cute, Clary."

"I'm not supposed to be cute." She grumbled.

"Doesn't Korra bend the elements?" Magnus asked.

Clary's face brightened. "She does. I'm so glad you know who I am."

Magnus shrugged. "Sometimes I watch children's television. I liked her story."

"Me too."

"All right, time to party! Have fun!" Magnus urged. "We'll have a vote for best costume." He leaned close to Jace. "By the way, yours really is my favorite." He straightened up and walked away, his arm wrapped around Alec's waist as he spoke with his guests.

Clary leaned into Jace as they looked around the room. "He has a soft spot for you."

"Yeah. And I can't figure it out. Somewhere along the way, I stopped pissing him off, I guess."

"I have a feeling it has something to do with your predecessors." She tapped one of his buttons. "Did you do this?"

He looked down. "Izzy did. Mixing the Herondale and Lightwood crests was her idea. Though I'm sure Maryse will have something to say about deconstructing an old coat like that. I don't even know how Izzy was able to find enough of each."

"Well, I like it. And you get my vote for sure."

Jace leaned in and whispered in her ear, "You sure you don't want to be the helpless girl locked in a tower and I come in on a white horse and save you from the demons keeping you hostage?"

Clary whispered back, "I am not helpless and I refuse to ever play that way unless you play it first." She stole a kiss and then sauntered away.

"It's a promise, Clary." He called after her.

She looked over her shoulder and winked. "Better be." She held out her hand.

He slipped his into hers and followed. He stayed glued to her side for the rest of the night.