Summary: A potions accident leaves Lily and Sirius trapped in each other's bodies! How are they going to be able to fool their friends that these two enemies are who they appear to be?

Disclaimer: Do you Sirius-ly (ha-ha) think that I own the magical world of Harry Potter? No – it all belongs to J.K. Rowling.

It was another typical day in Potions.

Sixth year Gryffindors Sirius Black, James Potter, and Remus Lupin appeared to be hard at work on their potions. Professor Slughorn had them working on various different potions, but even if they weren't doing that well, Slughorn wouldn't have cared all that much. His favorites were Lily Evans and Severus Snape, who both excelled at the class. At the moment the three Marauders were planning to bring Snape down a notch.

They had to wait until Lily wasn't looking – they didn't want her mad at them.

James strolled past Snape's cauldron on his way to the student cupboard and dropped some powdered Graphorn horn into Snape's cauldron. He continued on his way to make it look like he'd done nothing, and so didn't see Snape's potion turn an angry red and start to emit sparks and sputters. Sirius looked up upon seeing Snape back away from his cauldron as Lily moved closer to see what was happening. When the potion hissed, everyone ducked and tried to dodge away, but Lily was too close. Sirius jumped at her, trying to shove her out of the way just as the potion exploded.

0000000000000000000000000000000000000000000000000000000000000

'Oh my head!' Lily thought, as she opened her eyes, quickly squinting at the bright light flooding in through the windows. She groaned and a irate looking Madam Pomfrey came into view.

"Stay where you are, Mr. Black. I don't want you further injuring yourself. You know you and your friend Mr. Potter may need to have the Hospital Wing renamed after you considering how often you two frequent my domain."

"What?" asked Lily confusedly. She looked around and saw she was in the hospital wing, but she didn't know why. "Madam Pomfrey, what happened? The last thing I remember I was working on my potion…"

"Well, I'm not surprised," replied the hospital matron, "there was an explosion of Mr. Snape's potion, and you bravely, and somewhat foolishly, threw yourself in front of Miss Evans in an effort to save her. Alas, you were both drenched in the potion, and we are still unsure of the side effects."

Lily sat up so fast the room began to spin. When she had regained her equilibrium she asked, "Why do you keep calling me Mr. Black? What do you mean I saved Miss Evans – I am Miss Evans!"

Just then a beautiful redhead shot upright in her bed across the room, took one look at Lily, and screamed.

0000000000000000000000000000000000000000000000000000000000000000

"Well," twinkled Professor Dumbledore as he surveyed his two clearly distraught students, "it seems we have discovered what the side effects of the potion are."

Madam Pomfrey chuckled and Sirius shot her an angry glare, which was surprisingly more effective than it would have been in his own body. Despite her petite size, Lily Evans could be quite intimidating, even when Sirius Black was occupying her body.

"Now, now Miss Ev – I mean Mr. Black – there is no need to get upset. The potion Mr. Snape was brewing was not intended to have a shelf life of over two weeks, as it was meant to be ingested almost immediately after brewing. No doubt the potion will wear off within that time frame and you will both return to your original bodies," Professor Dumbledore explained.

Both students looked relieved, until their headmaster spoke again. "In the meantime, I would like you both to refrain from telling anyone about this switch. People might try to take advantage of you two."

Lily and Sirius wore identical looks of shock and horror. How on earth were they going to fool their friends into believing they were each other?

"See?" Dumbledore smiled, that damnable twinkle going into overdrive. "You are already acting like each other. Now, Madam Pomfrey says you are free to go, but I ask that you take a few moments to learn everything about each other so that you can play your parts accordingly, and then you may return to your house. Have a wonderful day!"

After Dumbledore left, Lily and Sirius stared stupidly at each other for many minutes.

Suddenly Lily ('Sirius') jumped up and grabbed her bag.

"Where do you think you're going?" Sirius asked her in a voice of forced calm.

Lily condescended to answer, "I already know all I need to know about you, Black. All I have to do is act like an arrogant, womanizing (here a frown of distaste appeared on her face for a moment) git for a few days. Oh, and use smaller words than I normally do."

Sirius glared, "And all I have to do is act like a frigid, know-it-all Ice Queen who wouldn't know a good time if it bit her on the bum!"

Lily stood there trembling angrily for a moment and stormed off.

Sirius called after her, "Just remember Princess, we've both got a reputation to protect, so don't blow it!"

00000000000000000000000000000000000000000000000000000000000000

About twenty minutes later Lily was wandering the corridors, still trying to figure out how to deal with this predicament and fuming over Sirius Black's comments.

"Padfoot."

How did that idiot land her in this mess? Because she was entirely sure this was his and/or the other Marauders' faults.

"Hey Padfoot!"

And how was she going to deal with being a boy for several days up to two weeks! And not just any boy, that arrogant, self centered, vain –

"SIRIUS!"

Suddenly, Lily remembered that she was Sirius. "What? Huh?" she looked around, only to find the bain of her existence walking towards her.

James looked at her with puzzled eyes. That is so cute, like a puppy –WHAT! – Evil thought! Bad thought!

"What's with you today, mate? I've been calling you for ages."

"Oh, sorry Po – James. I guess I've been out of it since that idiot Si – erm –Evans caused me to get drenched in that potions explosion."

James face darkened immediately. "Come on, Padfoot – you know we didn't mean for anyone to get hurt, not even Snivellus, and least of all Evans. She would never do anyone harm on purpose. Except maybe me." He mumbled the last sentence so quietly she almost didn't hear it.

Does Potter really think I would intentionally harm him? :Well, you don't exactly make it a secret you dislike him.: Yeah, but not that much.

James looked almost forlorn, but he seemed to want to shake it off, so Lily said what she thought Sirius would say. "Cheer up mate, she may come around yet."

James brightened instantly. "You think so?"

Just then a laughing Remus Lupin came up and slung his arm around James' shoulders. "Sure Prongs, just as soon as you deflate that head of yours a bit more."

They all laughed and headed to lunch together.

000000000000000000000000000000000000000000000000000000000000

In the great hall James looked to Remus, who was looking a bit pale and sad and said, "Three days Moony, than you'll be set for another month."

"Yippee," was all the response Remus could muster.

Lily was puzzled, as she had no idea what they were talking about, but tried to hide it as best she could.

This time it seemed to be James' turn to comfort. "Don't worry Moony – we'll be with you every step of the way." There were nods all around, even though Lily was still trying to figure out what was troubling Remus so much he had to have his friends with him 'every step of the way.'

00000000000000000000000000000000000000000000000000000000000000

Meanwhile in the Gryffindor sixth year girls' dormitory, Sirius was admiring his new body. "I gotta give Prongs credit, he has excellent tastes."

Sirius had spent the better part of the morning pouring over Lily's wardrobe – the majority of which now lay scattered all around her bed – and trying on various outfits. He currently had her dressed in a silky halter-top and denim mini skirt. He couldn't explain why he felt the need to do so – he simply had a compulsive desire to mix and match clothes.

Oh well, he thought, taking another bite of chocolate (he'd discovered Lily's secret stash in her trunk). Man, that is some good chocolate. Honeydukes sure knows their stuff.

Just then two of Lily's roommates came in. Alice Hart (soon-to-be Alice Longbottom – Frank had proposed in a fit of romantic insanity) smiled.

"Wow Lily – I love that look! A little more skin than you normally show, but no doubt an excellent date look," she said as she stripped out of her uniform, pulling out more casual clothes from her trunk.

Sirius gaped for a moment before remembering he was Lily and turning away. Frank is one lucky, lucky man.

Sirius decided to have some fun with his new body. "I'm thinking of going down to the common room and test driving this outfit."

Dorcas Meadowes, who had come in with Alice, spied the chocolate Sirius had set down on Lily's vanity and snatched it up before 'Lily' could stop her. "Are you sure you want to run out in a mini right now?" she asked between bites.

Sirius furrowed his eyebrows (Lily's eyebrows!) in confusion. Why not? Suddenly a painful cramp in his stomach nearly caused him to double over. Sirius thought he might be sick, and dashed into the bathroom. Less than a minute later there came a blood-curdling scream.

000000000000000000000000000000000000000000000000000000000000

Back in the Great Hall the four mischief makers had finished lunch and were slowly making their way back to the common room "Ah! I love free periods!" sighed Peter, talking about where they were going to explore in a few days. 'Sirius' was unusually quiet on the subject. Even Peter noticed.

"Why so quiet Padfoot?" he asked. "Got a girl on your mind?"

Before Lily could think of an appropriate 'Sirius' response, she saw herself come tearing down the corridor, screaming, "I'M DYING!" and heading towards the hospital wing in an outrageously revealing outfit. All of the Marauders looked at each other in confusion and went racing after 'her'.

They caught up with 'Lily' just outside the hospital wing. James grabbed her arm as gently as he could while still keeping a firm hold on her.

"Lily! What's happened? What's wrong?"

"Not now, Prongs! I'm hemorrhaging to death!" Sirius cried, wrenching his arm free and dashing into the hospital wing, calling hysterically for Madam Pomfrey.

The Marauders just stared at the doors for a moment.

"Did she just call me Prongs?" asked James in confusion.

Suddenly 'Sirius' burst out laughing – Lily had realized what was wrong with Sirius that would make him think he was dying. All the other Marauders looked at her like she was mad, and Lily struggled to control herself.

"I think – haha – I'm experiencing side effects – hehehe – from the p-potion accident." She quickly covered for her strange behavior. "I'll go see Madam Pomfrey and -- hahaha – check on Ev-Evans for you J-James."

With that said she headed into the hospital wing.

0000000000000000000000000000000000000000000000000000000000

"And you didn't think it was pertinent information to tell me it's that time of the month?" Sirius demanded.

Lily burst out laughing again, this time with Madam Pomfrey, who had taught Sirius the basic charms every young witch learns to aid in the pain of growing from a girl into a woman.

They didn't stop for several minutes, until Lily suddenly stopped, looking stricken.

"What is it my dear?" Madam Pomfrey asked worriedly.

Lily looked like a deer caught in the headlights. "I have to go to the restroom."

"…"

It took many minutes to stop Sirius from rolling around on the floor, laughing so hard he was crying.