DISCALIMER- I do not own any of the characters etc.

Similiarmus

"I want 3 rolls of parchment on the properties, uses and hazards of the potion you have just made on my desk by monday," the deep voice growled menacingly. "In case those Gryffindors among us haven't yet mastered the days of the week, that is 6 days from now." The black-cloaked figure slowly swivelled to face one student in particular. "We don't want a repeat of last week, do we Mr Thornton?" The scrawny third year, his hands still blistered from washing every cauldron in the dungeon (he hadn't handed in his homework, but how could he when one of the Slytherins had set it on fire, then tipped the ashes onto his head?) gulped and shook his head nervously. "Class dismissed" he called abruptly, and the entire class rushed to the door, silently thankful that they'd survived another potions class with that scary, greasy, bat-like professor Snape.

Snape sighed, brushing a strand of his midnight hair behind his ear. Third years had no patience, no appreciation of the subtle art of potions making. They were more interested in the cheap thrills of charms and, he grimaced, divination. His long, slender fingers delicately explored the area of his forehead which had been struck by a beaker when a first year's potion had exploded, propelling objects around the dungeons. That first lesson of the day seemed years ago now, yet the headache remained. Snape decided to take his anger, not quite fully vented on the aforementioned student, out on his last class: sixth year Slytherins and Gryffindors. "Perfect", he muttered evilly, and flicked through the textbook looking for the hardest possible potion to set them.

10 minutes later Harry Potter was sitting at his desk, determinedly not looking at Snape, who had numerous reasons to hate him, not least that he'd caught Harry looking through his most private memories last year. "Turn to page 467," came the hiss from the front, "today you will have one hour to prepare the 'deletris pulex' potion, any questions?" Snape's tone of voice made Harry look up, it was ominously gleeful. Snape's obsidian glare surveyed the room, obviously ignoring Hermione's hand waving in the air. "Very well, you may begin." Hermione, furious, whispered to Harry, "I want to know why we're doing this, we're not supposed to make this potion until next year!" before busying herself with ingredients. She may have been angry with Snape, Harry mused, but she was still eager to prove herself worthy of the challenge.

Three-quarters of an hour later, the reason for Snape's choice of potion had become abundantly clear: not only was the flea-removing potion fiendishly difficult to prepare (Harry had cut himself attempting to slice his willow bark into identically sized polygons) but it also smelt worse than Ron's quidditch kit bag. The entire class choked on the fumes as Snape stalked happily around the classroom, making snide comments about the quality of their work. Harry was prevented from wondering how the potions master seemed to be impervious to the odour by Neville's cauldron, which was making odd gurgling sounds. Distracted by the commotion caused by Snape shouting at his terrified friend, he failed to notice Draco Malfoy levitating a beaker full of bubotuber pus out of the student supply cabinet and directly towards his head. Realisation dawning at the last minute, Harry threw himself under the table, and the beaker (which had skimmed the top of his hair) made a neat landing: right in the middle of Harry's potion.

Silence descended on the classroom, as the whole class turned from Neville (who was nervously waiting for Snape to come back from his office with the book on elementary potions he was making him read as a punishment), to the smirking Draco, then to Harry, who was still under the desk. Approximately 3.4 seconds passed, and then Harry's cauldron blew up. The tawny coloured liquid, hurled through the air by the explosion, covered the entire class (bar Harry, safely ensconced under the table) from head to foot. Snape opened the door of his office, his best scowl plastered onto his face, ready to accost the perpetrator. Greeted with nothing but a thick haze of grey smoke, the scowl quickly changed to an expression of shock, and then one of pure rage.

Striding through the haze, he grabbed the first student he fell across. "Potter!" he spat, "what is the meaning of this?"

"But, s..s..sir, H..Harry's over th..there", stuttered the student, gesturing further into the gloom. "Very funny, Potter! 50 points from Gryffindor for you cheek, and it'll another 1,000 when I work out what THE HELL YOU DID TO MY DUNGEON!" Seeing the boy mumbling something else, but not really hearing throught the red mist of anger that had descended, he thrust the student aside. Drawing his wand he cried "Purgo!" and watched avidly as his spell cleared the smoke- hoping Potter had finally caused enough damage to get him expelled.

Unfortunately, what Snape did see only brought back his headache with a vengeance. The dungeons themselves were unharmed: the only actual damage seemed to have been done to a cauldron, which was lying in fragments on several desks. The main problem lay with the students, who were milling around the room with expressions of amusement, confusion or horror on their faces. Or should that be 'face', singular? Snape contemplated this problem for a while, every other part of his brain rendered unconscious by the scene in front of him. For what he was staring at, with his mouth wide open and a vein throbbing in his temple, was an entire classroom of Harry Potters. Six years of utter hatred for the boy who had crossed him more times than he cared to remember welled up inside of him and forced itself out through his mouth.

Many floors above, Albus Dumbledore sat in his office listening to the raw, guttural, interminable scream that could only have come from Severus Snape and mildly wondered what all of the fuss was about.

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Ok, this is my first fic, so please review- even if its just to tell me i should never write anything again! If anyone likes it I'll probably be writing some new chapters soon- should be fun with all the Harry's running around! (There might be slight snarry later- to be honest I haven't decided!)