A/N: Written for the Potions Competition.

6-year old Lily Potter was bored. She had played with all her dolls and doodled on some paper, but she was already out of things to do. And her parents were out of the house at some meeting too, leaving James to babysit his two siblings. Of course, he hadn't done anything of the sort. James had shut his door the moment they stepped out of the house, and hadn't come out of it since. She had already asked him to play with her, but he had said he was busy, and Albus was reading a book so she didn't want to bother him either. This led to her current situation, sitting on the carpet in the living room and staring into the fireplace.

Her face set into a frown, she wandered into her father's office. He had forbid them to go into there, and usually the door was firmly shut and locked, but he must've been in a hurry to go to his meeting because it was slightly open. Lily wondered why James hadn't noticed yet. Normally, he'd be the first one there and exploiting a possible prank situation but hey, it was his loss.

Lily's eyes travelled around the room. There were a bunch of interesting things in the room! There was a small hourglass that sat on a high shelf, a neatly folded cloak in the corner of the room, and a… blank sheet of parchment that sat on his desk. She ignored these and went to hop on the spinning chair in front of the desk. For a little while, she was thoroughly entertained, spinning around and around until her head felt light and dizzy. As she braced her hand on the desk, she saw a beaker filled with dark liquid. Squinting at it curiously, she decided that it must be coffee. Her mother had warned her about the liquid, telling her not to drink it until she was older. But Lily, feeling especially mischievous today, unplugged the lid, and downed the drink in all one go.

Getting up off the chair, she immediately felt funny. Her stomach was churning, and she could barely walk without stumbling even couple of feet. 'Bathroom.' She thought weakly. But then, as suddenly as the feeling came, it was gone. She still felt a bit weird though. It was as if the world was suddenly smaller. As she lifted her hand up, she brushed the top of the doorframe, something she couldn't have achieved a few seconds ago. Lily started sprinting for the bathroom, except she kept taking too small steps and ended up falling several times. As she frantically pushed open the door, she came to a stop in front of the mirror.

She screamed bloody murder.

James was planning a delicate prank. It was one that required intense concentration and carefully measured ingredients. He was almost finished, just the last touch and he was…

A bloodcurdling scream made him drop his dung bomb. James gaped, and then jumped up in irritation. It had to be Lily! There was no one else who would yell that loudly. Shoving his bedroom door open and charging down the hall furiously, he failed to notice that Albus had also joined him to see what the problem was.

"Lily!" James yelled, storming into the room. He stopped short suddenly, and Albus bumped into his back.

"What's the big idea?" He asked furiously, rubbing his nose. But then he glanced around his older brother and froze on shock. Because the person in front of him wasn't Lily. No, it was a red haired teenager. She was slender and thin, with huge brown eyes that were darting around in panic and orange-red hair that tumbled carelessly around her shoulders. Then, her eyes rested on them, and she started to calm down.

"James! Albus!" She cried happily, with a childish tone of voice.

James stiffened defensively. "Who are you and what are you doing in my house?" He asked cautiously.

Lily stopped short. "It's me, Lily." She cried, tearing up.

"L-Lily…?" James muttered. And it was true that he could see the similarities between the teen and his younger sister. It was like she was an older version of her. But how in the world did she end up like this?

"What did you do Lily?" Albus asked, almost dreading the answer.

Lily started sniffling. "I-I saw Daddy's office door was open, so I went in. And then I saw some coffee and wanted to see what it tasted like, cause Mommy never lets me try it. And so I drank it, and I felt dizzy, and then I saw what I looked like."

James stared at her incredulously. "Dad's door was open?"

Albus sighed. It figured that he would concentrate on that one thing. "Why don't we go check out the coffee then? It seems like that was what triggered the change." He said logically.

The three siblings followed Albus back to the study. Lily was clinging onto the back of James's shirt, which was a bit awkward for him considering she was now taller and older than him. They stepped into the room cautiously. James glanced at the vial sitting innocently on the desk. It was completely empty. Turning it around, he squinted at the tiny label at the bottom. It read, 'Ageing Potion'.

His mouth opened, but he couldn't seem to form any words in his shock.

"What is it?" Albus asked. "Did you find out what happened?"

James snapped back into focus. "She drank an Ageing Potion."

Albus fell silent while Lily cocked her head in confusion.

"I'm sorry, what did you just say?" He managed to stutter out.

"I said Lily drank an Ageing Potion." James snapped. Inwardly though, he was panicking. Oh my gosh, I'll be grounded for life. Mum and Dad will ban me from going to Hogwarts and my life will be ruined!

"What's an Ageing Potion?" Lily asked in confusion.

Albus, being the ever-present bookworm, responded immediately. "An Ageing Potion, as the name suggests, ages you. How much you age is directly proportional to how much you drink." He gave his younger sister an appraising look. "Judging by how old you look… I'd say you drank the whole thing."

"Well when is it going to reverse back?" James asked frantically.

Albus shrugged. "A couple of hours at least. We should watch over Lily until then."

James nodded in response. "Got it Lily? You are not to leave our sight until you return back to normal."

However, when they turned back to check for her confirmation, she was gone. The two brothers were left looking at empty air.

"Where did she go?!" James shrieked.

A happy giggle and the sound of the door slamming was his only answer.

Albus's eyes widened. "Lily, get back here!" He yelled, sprinted downstairs with James right on his heels. Jerking out of the door he watched, horrified, as Lily headed towards town.

James cursed. Under any normal circumstances, he would've been able to easily out-run his baby sister. But she was now a 16-year old with longer legs. The only advantage they had was that she was unused to having a larger stride so she wouldn't be able to travel as far.

Suddenly, Lily bumped into a boy standing on the street. He glanced at her in disinterest, then did a double-take. Ruffling his hair, he smiled at her.

"Hey. My name is Sebastian. What's yours?" He asked.

It was then that James and Albus caught up with her.

"It's nothing!" James blurted out.

Sebastian looked down at them. "Oh, so you have little brothers?"

Albus wondered if this guy was an idiot. He must be some kind of moron to not notice that they were Harry Potter's kids.

"Whatever. Lily, we're going!" James said in exasperation.

But it was too late. More guys had noticed Lily and were flocking around them, blocking their escape. Their voices were steadily rising, trying to be heard above the crowd. They were now jostling them around, trying to reach the girl. James glanced around the sea of bodies in panic. There!

Grabbing Lily and Albus's hand, he sprinted for the small gap that appeared. It was a good thing that the group of boys were too busy arguing that they didn't notice them escaping. As soon as they were a good distance away, James slumped down on a bench and rubbed his temples.

"Let's go home now." He said.

Lily's eyes widened. "But I don't want to go home yet!"

James and Albus stared at her.

"Why not?" Albus asked.

"Because being grown up is fun!" She replied happily, swinging her legs.

James sighed. There was no way for him to force her to come with them seeing as she was physically more mature now. "Fine." He hissed. "But you have to stay in our sight at all times, clear?"

"Okay!" Lily agreed immediately.

So for the next three hours, the siblings spent playing in the park and avoiding all human contact. Soon, Albus glanced up at the setting sun.

"It's about dinner time." He muttered to James. "Mum and Dad will be coming home soon. The potion should also be wearing off soon."

James nodded. "Lily!" He called. "It's time for dinner so we have to go home now."

The teen jumped up from where she had been inspecting a flower. "Coming!" she shouted back.

As they began walking back home, Lily tripped… and landed on the lap Sebastian, who was sitting on a park bench and reading. He glanced up at the girl on his lap and grinned.

"I was wondering where you went." He purred. "Anyways, I was wondering if you want to go out sometime?"

But he never got his answer as there was a small poof and suddenly, there was a giggling 6 year old sitting in his lap. He stared at her, bewildered.

James grabbed her now smaller hand, and sprinted out of there.

There was a small pop as two people apparated onto the street. These two were none other than Harry and Ginny Potter. And for a moment, they stared at the silent house in front of them.

"Do you think it was a good idea to let James babysit Albus and Lily?" Ginny whispered. "Look at how quiet it is."

"I'm sure nothing happened." Harry replied easily.

Opening the door to Lily's room, the two parents smiled softly at the sight of their children all fast asleep on Lily's bed. The next day at breakfast, Harry glanced at Ginny and she nodded.

"James," Harry began. The boy in question paled. "Your mother and I were thinking that since you did such a great job watching over your siblings yesterday, if you would want to do it again?"

"NO!"