Spoilers: This story begins shortly after the scenes depicted in Snape's Worst Memory, OotP. There are also some tie-ins to PoA.

Notes: I skimped on the introductory descriptions of each character. After all, you're reading a fanfic. The characters are already alive and well in your head. This story was inspired by a thread discussion about Snape's Worst Memory and why it wasn't the night he met Mooney in the tunnel under the Whomping Willow.

Disclaimer: While this story is mine, all recognizable characters and places are not. Original credit for those goes to J.K.Rowling.

A Prank for a Prank

Chapter 1

Late afternoon sunlight lit the dormitory of Gryffindor Tower. Sirius sorted through his trunk for the third time. James lounged on his bed, idly watching Sirius and twiddling a quill between his fingers. "What are you doing?" he asked at last.

Sirius looked up. "My shampoo is gone." James chuckled until his friend's face darkened.

"Sorry, mate. They have shampoo down there." Sirius sighed and stood up.

"I know," he studied his trunk, "Do you think Wormtail nicked it?" James laughed again. Laugher was easy this afternoon. The school year was coming to a close and O.W.L.S. had proven easier than he'd been led to believe. "I wouldn't put it past him," Sirius said, smiling down at his best friend.

"Padfoot, Eva doesn't care about your shampoo."

"I know." Sirius gathered up his stuff. "I'll be back," he said as he left the tower room for the showers.

"I'll be here!" James called after him.

Sirius made his way through the corridors to the shower room. Thoughts chased through his head. It was only three more nights until the full moon! One last romp before summer holidays began. To pass some of the time, he was meeting Eva just outside the library after dinner. His heart skipped a beat at the thought of her. Two girls he passed in the corridor smiled at him. He tried hard to ignore them. He was so sick of simpering girls throwing themselves at him! Maybe that's what made Eva special. She never simpered or fawned over him. She treated him normally.

He stopped in the doorway of the shower room. A pale, skinny boy stood with his back to the door. "Too perfect," he thought. "Snivellus!" he called. The dark-haired boy spun around. An evil glare spread across his face. "I didn't know you showered."

"Keep away from me, Black!" he hissed. Severus gathered up his stuff, never taking his eyes off of Sirius. Sirius smiled wickedly at him. An evil glint burned in his gray eyes. He folded his arms, clutching his stuff in one hand.

Snape started for the door. He sneered at Black, "Out of the way." Sirius stood his ground.

"Or else?" he prompted. Snape did not answer. "No wand, Snivellus?"

"You don't have one either," Snape replied. Sirius thought about that for a moment.

"You're right," he sighed melodramatically, "I'll just have to use force." He dropped his stuff and stepped into a fighting stance. Snape paled and suddenly pushed passed him. He was no match for Black physically. Sirius laughed as he rushed out. "You forgot to wash your hair!" he called as Snape disappeared down the corridor.

Sirius stooped to pick up his stuff. "My day is now complete," he thought. He moved around the corner, out of sight from the door. Low shelves lined the walls. He set his towel and clean clothes down. Then he looked around for the shampoo. Finally he found the only bottle and undressed.

He showered quickly, dried off and draped the towel over his wet hair. After dressing in tight black jeans and a crisp, white, shirt, he gathered up his other clothes and made his way back to Gryffindor Tower.

Pulling the towel off his head, he gave the password and waited for the Fat Lady to swing open. A group of first year girls sat giggling near the fireplace. They gaped at him as he entered. Sirius turned quickly and headed for the boy's dormitory. "Silly girls," he muttered as he climbed the stairs to his room.

"Close the door before my snitch escapes," James called as he entered. James, apparently, hadn't moved. He still lay on his bed. The quill sat forgotten on his bedside table. His hazel eyes tracked the movements of a small golden ball as it flitted around his bed curtains.

Remus had come in while Sirius had been out. He was unpinning his prefect badge. "What? No studying?" Sirius asked him.

"Ha ha," Remus answered. His hands shook as he closed his trunk. A pang of concern ran through Sirius. His friend seemed so wan and pale in the fading sunlight.

"Are you alright?" he asked, all joking now gone from his voice. Remus rubbed his face and sighed deeply. He looked over at Sirius. A strange, half-horrified look engulfed his face. Then a wild laugh broke from him. He doubled over with the effort to suppress the laughter. James looked away from the snitch.

Laughing, he said, "That's a new look for you, Padfoot."

Horror flashed through him. Sirius leapt for his mirror. Remus was catching his breath, regaining control. James came to stand beside him, his reflection laughing silently. Once black, Sirius' hair was now a livid green; the color of young caterpillars. James' merriment died as Sirius' face darkened. Remus came to stand beside them. The look on his face matched James'; concern and anger on their friend's behalf.

"Who do you reckon did it?" Remus asked.

"Snivelly," he hissed.

"Snape?" Sirius turned to Remus.

"He was leaving the shower room just as I arrived."

"We'll get him," James promised. Sirius turned from the mirror. He unbuttoned his shirt sleeves and rolled them up to his elbows. Then he grabbed his wand.

"We'll get him, alright. Right now!" He stalked towards the door. James and Remus followed him. As they descended, they came upon Peter. "Hey, Sirius. What happened to your hair?" He asked. He turned around and fell into line behind Remus. "Where are we going?" No one answered him.

Sirius charged through the castle; a dark storm cloud, full of anger and hatred. This was going too far! That whiny coward! That GIT! A low growl was building in his throat, a snarl pulling at his lips. He ran down the last few stairs and crossed to the Great Hall. Everyone was at dinner.

"Wait!" James grabbed him, pulling him to a stop.

"Let go!" he roared.

"We can't do it in there! The Teachers!" James spun Sirius around to face him. "Let's wait for him to come out. Maybe," he paused, licking his lips, "Maybe we can do something about your hair while we wait."

"If Snape used a potion we'll have to use an antidote," Remus put in. James spared him a quick glare. Remus held up a hand, backing away.

"Come on Padfoot," James pulled him back towards the broom closet. He kept a hopeful smile on his face. Sirius followed him into the closet. They hunkered down in amongst the brooms and mops. "Keep watch, Wormtail," James instructed. Peter bounced up and down on his toes as he peeked through the door. James pulled out his wand, staring at Sirius' green hair. After a moment he tapped him on the head. The green flared neon, but did not return to black. He stuck one end of his wand in his mouth, sucking on it as he thought. "What do you think, Mooney?" he asked after a minute.

A wry expression crossed Remus' face. He leaned forward from his perch on a mop bucket. "Well, since you're asking, a simple antidote will put him right. I can mix it up easy enough. See, when you use a potion to change something, you need an antidote for it." James looked up at him, catching the sarcasm in his voice. He smiled, laughter warming his hazel eyes.

"Just do it," Sirius growled. Remus stared at him for a second.

"I'll go now, shall I? While everyone's at dinner." Remus slipped out of the closet and disappeared in the direction of the potion's classroom.

The three friends sat brooding in the dark. The bar of light from the Great Hall fell across Sirius' face, bathing one eye in light, leaving the other in shadow. His anger slowly ebbed. James studied him in the gloom. Often, he could judge his friend's anger. It lay close to the surface tonight. They could hear people leaving the hall, making their way to the dormitories.

"He's coming!" squealed Peter, ducking down. An anticipatory giggle accompanied his words. He looked eagerly at Black. James watched the anger flare again as his friend rose slowly. He gripped his wand tightly. James rose with him. Sirius glared, "Are you going to stop me?" he whispered. James stepped aside as best as he could.

"After you," he invited with a bow. Sirius flew from the closet and slammed into Snape with a roar. His momentum carried the two of them into the opposite wall. James sauntered over as Sirius grabbed Snape and slammed him into the wall again. Peter followed at James' heels, attempting to saunter as well.

Sirius' wand pointed straight at Snape's dark eye. His forearm pinned him by the neck and shoulders. "Bad move, Snivelly," James purred. Snape only had eyes for the tip of the wand. James flicked him on the forehead with his own wand. Snape's eyes pulled away from the wand tip, glaring at James instead. They stopped on Sirius' hair, widening. His thin lips twitched as he fought not to smile.

"Go on then," Sirius hissed in his face, "Smile. Just one hint of laughter. Give me a reason and I swear I will take that smile off your face!" Snape schooled his face from laughter to concern.

"Why, Black," he said, "What on earth have you done to your hair? Surely the girls will be less likely to throw themselves at you now?"

"You know damn well what happened to my hair!" Sirius bellowed in his face. More students were leaving the Great Hall. The stopped to watch, forming a crowd.

"You know," James began, "I think Snivel would look quite fetching with pink hair." Peter laughed. Sirius smiled.

"Try it out," he offered, relaxing his hold on Snape. Snape struggled then. He pulled out his own wand.

"Expelliarmus," James said, absently. The wand flew away into the crowd. He tapped Snape on the head. His hair went from a greasy black to lanky, candy pink. The crowd's laughter rang through the hall, punctuated by Peter's hysterical giggles.

"Well, now you're even." Remus' voice cut through the laughter. He held a large flagon of potion in his hands. Sirius and James looked over at him. Nodding slowly, Sirius released Snape. With a snarl, Snape dove for his wand. James tracked his movement. He snatched up his wand and spun towards his tormentors. James crouched into a dueling stance. Nostrils flaring, eyes wild, Snape pointed his wand steadily at James. He opened his mouth to speak.

"Make way!" Filch's gruff voice called through the crowd. James stood up hurriedly as Snape, glaring, lowered his wand.

"Tsk, tsk, tsk," James shook his head, "Playtime's over." James turned and led the way up the stairs.

"See you around, Snivellus," Sirius called, looking over his shoulder as he ascended the stairs. Remus lingered for a moment, watching Snape. Then he too left.