Magnus had been rummaging through magical artifices and ingredients for potions all morning, that until a certain blonde shadowhunter knocked on his door.

"Sorry, it's not Alec" said Jace as greeting when Magnus opened the door for him.

"What do you need?" asked Magnus, politely.

"Polyjuice potion" answered Jace, smirking.

"So now he knows Harry Potter" said Magnus, rolling his eyes at the shadowhunter as he opened space for him to come inside.

"I need to ask you a few things, there was an attack and we can't identify the demon" explained Jace, entering the apartment.

"Alright. But first I have to do something. Don't touch my things" said Magnus, walking to his bedroom.

Jace nodded and plopped down on the couch. Didn't take long for him to get bored, so he decided to check on what Magnus had been working on.

Jace was examining a little bottle filled with a blueish liquid that had an awkward shine to it. Distracted as he was by his curiosity, he didn't notice that the bottle's cap was unscrewed and suddenly its content was all over his front.

"Oh, shit" he said, looking down at his stained shirt. Soon, he began to feel really weird. Everything seemed to be bigger and growing even more around him. He felt slightly dizzy and his mind was clouded. Jace closed his eyes for a brief moment and when he opened them again, he was sitting on the floor, with his now over sized clothes hanging on his body. He didn't know where he was and he was all alone, what made tears well up in his big golden eyes.

"Mommy? Alec? Izzy?" called Jace, whimpering softly. When no one answered, fat tears rolled down his cheeks and he began to cry loudly. Magnus ran back in the room hearing the cry and got completely shocked. Instead of Jace, there was a toddler in his living room. And worst, the toddler was sobbing. Well, damn.

"Uh, hello, little one" said Magnus, softly, trying not to scare the already upset child.

"Who you?" asked Jace, between sobs.

"I am Magnus. Why are you crying, darling?" said Magnus.

"I want my Mommy" answered Jace, "Magnus friend of Mommy?"

"Well, yes, Jace. I am a friend of your Mommy, but mostly of your brother" said Magnus.

"Alec?" asked Jace, seeming to cheer up a bit at the mention of his brother.

"Yeah, Alec. Let's call him?" asked Magnus. Jace nodded and raised his arms to be picked up. Magnus smirked and lifted him in his arms, then balanced him on his hip and got his phone, quickly dialing Alec's number.

"Alec, sweet pea! Thank God you picked up the phone. Listen, I need you to come over.." said Magnus, trying not to worry Alec.

"Magnus, did something happen? I'm a bit busy right now, I don't know if I can leave.." said Alec through the phone.

"Well, I'm afraid it's a bit urgent, Alexander. It's about your brother" said Magnus, looking at the little Jace.

"Jace? What happened?" asked Alec, worry clearly on his voice.

"It's, uh, complicated" answered Magnus, biting his lower lip.

"Magnus, you're worrying me" said Alec.

"Jace is under the effect of one of my potions" said Magnus, as quickly as he could.

"By the Angel, which potion Magnus?" asked Alec, now getting nervous.

"He's a child now. Temporarily" explained Magnus.

"He's what?! Damn it. I'm on my way" said Alec, hanging up the call. Magnus stuffed the phone back in his pocket and looked at Jace.

"Well, little one, it honestly went better than I thought it would" he said.

"Alec coming?" asked Jace as Magnus put him back on the floor.

"Yes, Alec's coming" answered Magnus, sighing.

A few minutes later, someone knocked on the door and Magnus went to open it. Jace was distracted playing with Charmain Meow's tail, but he turned his head to see who was coming as Alec, Clary and Isabelle entered Magnus's apartment.

"Oh my gosh" said Clary, placing a hand over her agape mouth. Alec had told her and Isabelle what had happened to Jace, but she wasn't prepared to see her boyfriend suddenly as a toddler. Jace got up as he saw Alec and ran to him, hugging his legs to get attention.

"Alec, Alec" he piped up, excitedly.

"Whoa, hey there" said Alec, picking Jace up. At this point, the little boy had only the t-shirt he was dressing earlier covering his body, as the others pieces of clothing were too big to stay on him.

"As I was explaining, he only recognizes the people he has bonds since a very long time, like you, Isabelle and your mother, and that's all he remembers. I was working on this potion, so I still don't have the antidote… I'm sorry, I should've been more careful with my stuff" said Magnus.

"It wasn't your fault, Magnus" said Alec, "we will take care of this"

"Yeah, it's okay. Now I finally can choose Jace's clothes without him complaining" said Isabelle, smiling at the blonde toddler in her brother's arms.

"Izzy!" said Jace, grabbing the air towards her.

"Hi baby, c'mere" said Isabelle, picking him up and cradling him on her hip.

"This is so awkward" muttered Alec.

"Look Jace, this is my friend Clary" said Isabelle, approaching the red head.

"Hello, Jace" said Clary, smiling softly at the little boy. It was impossible not to smile, he was just adorable.

"Hi Clary. You pretty" said Jace, giving her a cheeky smile. Everyone laughed as Clary blushed almost to the color of her hair.

"Even with this age he still does this to you" said Isabelle, tickling Jace's tummy and making him let out a delicious, contagious laughter.

"Talking about age… How old is he?" asked Clary.

"I don't know, biscuit. I didn't think about asking him" answered Magnus, frowning.

"How old are you, Jace?" asked Isabelle. Jace lifted two little fingers for her.

"Two? Oh, you are a big boy, hm?" said Clary, and Jace nodded happily.

"Jace is a big boy!" said Jace, wriggling in Isabelle's arms to go to the floor. Isabelle put him down and turned to Alec.

"We need to tell Mom" she said.

"She'll go crazy" said Alec, "but you're right"

"Hey Magnus" called Clary, "did you put a diaper on Jace? He's two, probably he still uses them"

"Good idea, biscuit" said Magnus, summoning a box of diapers. "All yours"

"Oh, get some clothes for him too" said an overly excited Isabelle, while Clary opened the box of diapers and got one.

"Do you know how to do this?" asked Alec to Clary.

"I used to babysit kids to get some money for my art supplies, so yes" she answered, picking up Jace and carrying him to the couch.

"Jace, I'm gonna put this diaper on you, alright?" said Clary, laying Jace down on the couch.

"Okay Clary" answered Jace, playing with one of the colorful pillows. Clary lifted his bottom and placed the open diaper under him, then pulled its front between his little legs and closed the tabs.

"All done, little man" she said, tickling Jace's tummy.

"Thanks" said Jace, giggling and squirming to get away from the tickles.

"Clary, here, Magnus got some clothes for Jace. Can you get him ready?" said Isabelle, handing Clary a pack of simple white, long sleeved baby onesies and gray cotton pants along with socks and a pair of black mini Converse shoes.

"Sure" answered Clary, opening the pack of onesies. The packaging said they were size 18 months, but as Jace was little for his age they would fit him perfectly.

"Alec, let's call Mom and prepare her" said Isabelle, pulling Alec by the hand to the kitchen.

"Let's get you dressed then, Jace, come on" said Clary, taking the black T-shirt that belonged to her teenager boyfriend off of the small boy in front of her. While she folded the shirt and took it to her nose to smell Jace's scent, the toddler version of him started jumping on the couch, only in his diaper. Smiling, Clary picked him up and sat him on her lap, then carefully slid the open onesie down his head and little arms and arranged it on his torso.

"Lie down now, baby" she said, and Jace quickly obeyed, lying down with his legs on her lap. Clary got the buttons properly fastened up and slipped the pants on Jace, then finally moved to get his socks and shoes on.

"Alright, let me look at you" she said, making Jace stand up on her legs. "Aw, what a handsome little boy we have here"

Jace smiled cheekily and settled down on Clary's lap again, resting his head on her chest.

"Are you tired?" asked Clary, already knowing the answer. Jace shook his head, but soon enough he let out a big yawn and snuggled up on Clary's chest.

"We're ready to go!" said Isabelle, entering the living room again.

"Shh, Izzy! Jace's almost sleeping" said Clary, getting up and shifting Jace in her arms, so now he was resting his head on her shoulder and his legs were wrapped around her waist.

"Whoops, sorry" said Isabelle quietly, approaching Clary and brushing Jace's hair away from his eyes.

"Izzy, I want Momma" said the sleepy little boy.

"We're going home now, okay?" said Isabelle, smiling at her brother as he nodded.

Okay, so what do you think about this? RR xoxo