Chapter three of god knows how many. If you have something you'd like to inflict upon a fictional character with no chance of being sued or cursed into oblivion, e-mail address is:

underthefloorboards@hotmail.com

On a Thursday afternoon, Slytherins and Gryffindors had double potions together in the dungeons. The teacher at the time, Professor Jigger, was a daft, balding old man, who barely knew where he was most of the time.

Which is exactly why Severus Snape and Sirius Black got away with most everything in his class.

Today, they were making a Truth Draught, which was to be bottled and given to Jigger before the end of the lesson.

Now. Snape happened to know more about potions than Jigger himself, and had already planned his revenge on Black for hexing his robes the previous day. The hex, which was a particularly wicked find of Black's, made Snape's robes fly up over his head whenever a girl walked past him. Much to the horror of Professor Mc Gonagall in Transfiguration, where they stayed up over his head the entire lesson.

Sirius and Remus were paired together, and were situated beside James and Lily.

Remus, as always, had lined his ingredients along the table, in order of addition to the Potion. Snape knew, that if the miniature marshmallows and the powdered scarab beetles were switched, the Truth Potion would turn into something decidedly more interesting. Under the pretence of getting more water from the fountain on the wall, Snape sneakily switched the ingredients, and finished his own potion quickly, so he could watch the show.

Sirius was dancing like a shaman around his cauldron, muttering weird made-up words under his breath, much to the delight of James and Remus, who were bent double in laughter. Lily was watching with a disdainful look on her face. Sirius grabbed the marshmallows and the beetles, and carefully added them in the order Severus had planned.

Leaning back on his desk, Snape watched the violent pink potion erupt, geyser-like, out of Black's cauldron and hit him squarely in the face. Spluttering in surprise, Sirius looked round at James and Remus for help, but stopped in mid-turn. There was a noise like a plunger in action, and Black squeaked, snapping his thighs together. James, Remus and Lily watched as he tried to run out of the classroom moving only his lower legs. He managed it, however, and wasn't seen for the rest of the day.

Rumors started as to the whereabouts of Sirius Black. It was common knowledge that he had returned to the dormitories, and locked himself in a bathroom.

What was not widely known was that Remus and James had taken him to the Hospital Wing in the early hours of Friday morning.

Sitting at the Slytherin table, Snape sat smugly in the knowledge that, is the potion was allowed to work for long enough, the results would be irreversible. Someone tapped him on the shoulder.

"Professor Dumbledore?" Snape was rarely addressed directly by the Headmaster.

"Could I have a word please Severus?" he asked politely, and Snape followed him out of the Great Hall.

They walked in silence for a while, until Severus realised they were heading towards the Hospital Wing.

"You have potions class with Sirius Black, don't you?" Dumbledore asked him, as they walked past Peeves making  suits of armor do the tango.

"Yes sir." Answered Snape, avoiding a wasp that had flown through the window.

They reached the Hospital wing. Pushing the door open on the surgical cleanliness, they walked towards a bed with the curtains pulled around it.

"Mr. Black has sustained some rather, unusual, injuries from a awry potion. Professor Jigger cannot remember there ever being a disturbance." He whispered softly. "As you would be the most talented student at Potions, I was hoping you could give a diagnosis." Dumbledore smiled. "I have never been very good at Potions." He added, pulling back the curtains.

It was all Snape could do to not collapse with laughter.

Sirius was sitting up in the bed, clutching the covers around his shoulders and looking severely depressed. James, Remus and Lily were sitting along one side of the bed, also trying desperately not to laugh.

"Um…" said Snape uncertainly. It was quite hard to know what to say. "What happened?"

Sirius snorted derisively. "Doesn't really tell me much." Snape retorted.

"I'll leave you to it, then." Said Dumbledore, sidling out of the room.

"What are you doing here?" hissed James.

"Dumbledore wants me to find out what went wrong with Black's potion, and then make a antidote." He sneered. "Believe me, I did not beg to help."

Looking slightly less hostile, James turned to Sirius.

"Tell him what happened." He asked gently.

Sirius shook his head arrogantly. "The quicker you tell him the quicker he can get an antidote." James said cautiously, eyeing Black as though he would launch into a killing spree. Black burst into tears. Looking thoroughly shocked, Remus handed him a box of tissues.

"Thank you." Black sniffed, pulling out handfuls of tissues.

"He's feeling a bit hormonal." Explained Lily, with a sympathetic look on her face. Remus was holding his hand now.

"It's ok, Sirius, I'm not much fun to be around a few days in the month either."

"Pardon?" Snape exclaimed. "Is he…" he trailed off, gesturing at Black. Lily nodded. Snape grimaced.

"How?" Apparently this was the wrong thing to say.

"You don't understand me!" Black screamed, chucking the tissue box at him. "You have no idea how it feels to be a woman!" Dissolving into tears again, Black continued to mumble about sexism, until Remus had him halfway sociable again. Flicking hair out of his eyes, Sirius tied it back in a ponytail, but when he raised his arms, the covers fell off his chest. He was wearing one of Lily's bras, a deep burgundy color, with a small floral print on the straps. James couldn't help himself. Falling off his chair with laughter, James clutched his stomach as he continued to roar with laughter. Snape could easily see what was so funny. Sirius had retained the musculature of a well-built young man, six pack and biceps like bowling balls, but he had grown a pair of breasts, contained in a floral bra. Pouting, Black flung back the covers and announced,

"I'm going to the bathroom!" in a wavering voice, and he grabbed a packet of Tampax from the bedside table, and strode off to the toilets at the end of the ward. Seeing him out of bed reignited the hilarity of the situation and James started laughing hysterically again.

Sirius was wearing panties to match the bra.

That was perhaps the strangest thing Snape had ever seen. The most athletic boy in the school, with a body to rival Arnold Schwarzenegger, having breasts, wearing a bra, panties stretched over broadened hips, and having absolutely no sign of  a bulge where should be a bulge.

James had just about calmed down, when a voice came from the toilets.

"Lily?" Lily looked horrified.

"Yes?" she answered reluctantly.

"How do you use these?" he called, sticking his hand out the door. Dangling threateningly from his hand, was a tampon.

"There's a diagram on the packet." Called Lily, pleading mentally not to have to show him.

"Yeah, I know, but I don't understand it." He answered, and paper rustling could be heard. "Where's the vagina?"

Lily stood, and took something out of her bag. Walking quickly towards the toilet door, she passed it through to Sirius.

"Use that instead." She said, and started walking back towards the bed.

"What the hell's this?" he screeched, sticking his hand back out the door. He was holding a sanitary towel.

"Peel off the papery bit." Replied Lily. There was more rustling.

"Now what?"

"Now stick the sticky bit onto your pants." She answered.

After a short pause, Sirius emerged from the bathroom. James rocked back and forward in convulsions of laughter.

Sirius had indeed stuck in on his pants. On the outside, horizontal along his stomach.

"How does it work like that?" he asked, completely confused. Lily explained it to him again, and he fixed it quickly behind the bed curtain. Jumping back into bed, he looked slightly put out. "How can you do that every month?"

Lily rolled her eyes.

"Do you know what's wrong with him yet?" asked Remus. Severus had taken a book from his bag and was reading a page labeled, 'Mistakes and After-Effects'.

"I think he may have mixed up the addition of scarab beetles and miniature marshmallows." Answered Snape, pretending to sound as though it had just occurred to him. "That would result in a highly volatile potion that reverses the gender of the maker."

"Sounds about right." Said James.

"However…" he mumbled.

"What? What is it?" shrieked Sirius worriedly.

"If the potion is left to work for long enough, it may be irreversible." He continued, feigning a look of concern.

"Well get to work!" screeched Sirius, "I don't want to be stuck like this!"

"You know why they call it a ponytail, Black?" snarled Snape, gesturing at Sirius' ridiculous hair, "Because there's always an arsehole underneath."

SLAP. SLAP. Sirius was kneeling on the bed, with a hand poised to slap him again.

Snape didn't move.

"He's trying to help, Sirius." Placated Lily. This seemed to make Snape even angrier. Throwing down the book, he donkey-nipped Sirius on the nipple. Howling in pain, Sirius recoiled back towards Lupin. Black made another lunge for Severus when he went to pick up the book, but James grabbed him around the waist and pulled him back.

Snape sat while Lupin talked to Sirius.

"Snape? I mean, um…Severus?" said Black in a small voice.

"What?" he replied angrily. He still had a red hand-mark on his face where Sirius slapped him.

"I'm sorry for slapping you. And being arrogant and ungrateful. I know you're just trying to help, and I appreciate it." He mumbled. He extended a hand. Lupin grinned happily. Shaking it quickly, Severus launched into an explanation of how the potion would turn him back.

"The obvious stuff will return first." He said uncomfortably, not wanting to talk about Black's genitalia in any way, "and then all the hormonal stuff will dissipate over the space of about an hour."

"I'll still bleed?" shrieked Black. Severus nodded. "Out of…?" he whined. Severus nodded again.

"I'd better get going. It's quite a complicated potion." He said quietly, and walked off towards the door.

Returning about an hour later with a goblet full of the potion, Severus was greeted with the sight of James feeling Sirius' breasts. Sirius was giggling girlishly, telling James to, 'move a bit to the left…no right…there! Do that again!' e.t.c.

Coughing to announce his presence, Severus handed Black the potion, and told him to drink it all at once.

Gulping it down, the 'obvious stuff' happened immediately.

Sirius' chest seemed to deflate, and he quickly wrenched the bra off himself. There was a ripping noise.

"I don't think panties are designed for men." Said Sirius unnecessarily, as everyone except Remus averted their eyes to him pulling off the panties and bending down to get boxers from a bag beside the bed.

Chatting amiably to James, Lily remembered something.

"Sirius! You're still…the blood!" she yelped, handing him another sanitation device. Skittering off to the bathroom, Sirius affixed said item inside his boxers, and emerged smiling. Gathering his books, Snape made to walk back to the Slytherin Common Room, but Sirius stopped him. His eyes were watering, and he fanned at his face with his hands as he gushed thanks and gratefulness at Snape, who remained impassive. Finally bursting into hacking sobs, Sirius flung his arms around Snape, and cried all over the shoulder of his robes. Remus looked highly amused, and James and Lily made 'Awwww' noises as Snape felt extremely uncomfortable and reluctantly put an arm around Black, patting him cautiously on the shoulder.

Wrenching Sirius off him, Snape held him at arms length, while the tears subsided, and Black's face returned to it's normal tanned color, instead of the beetroot red it had been throughout his crying session.

Still thanking him for all his hard work and 'I know you don't like me that much but I appreciate it that would you would help', Snape turned to go, but Black grabbed onto his arm and spun him around, planting a kiss on his cheek.

"Thanks." He said coyly, blushing and giggling.

Awwww. A lot longer than the previous chapters, but I think Sirius Black getting breasts and periods is too much fun not to drag out.

Oh. By the way, if you don't know what a donkey nip is, it's when you get a bit of skin and flesh between your forefinger and thumb and twist it around. It's bad enough on your arm, but it's almost unbearable on nipples.

And the 'sanitation device' thing, that's what one of my friends call tampons and pads and stuff. She's a bit weird sometimes.

Xanadan