Disclaimer: See previous chapter. Oneshot. Thing.

I could have decided to simply string all of these together, making this chapter three of Mistaken Identity, but I'm quite lazy, a fact you should already have gathered from the length of chapters and disparity in dates between publishing and update. That, and there are a great variety of clichés that could have occurred between MI and the beginning of Harry's magical education, and there is always the option that I may one day decide to do something stupid like follow up on those opportunities.

Snape had been preparing for the Dunce Who Lived's arrival at Hogwarts ever since that fateful Halloween night he'd realised there were only two other people who knew Harry Potter was the true defeater of Voldemort, and that one of them was a sentient hat, and the other a flaming chicken.

Quite aside from hating the Dunce Who Lived on principle as the spawn of James Potter, Snape had anticipated that the blatant favouritism demonstrated by the woefully misled parents would in the interim craft Dunce into a child truly worthy of his derision, even were he not genetically related to Potter. He'd been proven right.

Naturally, he was under orders from Dumbledore to protect the loathsome worm, but, Snape reasoned, he already had one Potter under his wing – the better Potter, Merlin forgive him for putting two such words together – and besides, Dumbledore never said anything about making him miserable.

Snape, it can safely be assumed, despised children. Most teachers do, but Snape had elevated it to a state well beyond normal boundaries. With his rather unique training in certain areas of magic and absolutely nil instruction in the area of teaching, Snape was to education what Voldemort was to life insurance. It had been eight years since the last official complaint against him, which said much for his campaign of intimidation.

His plan of torture got off to a flying start. He'd bribed Peeves with several explosive and luridly coloured potions to disorientate Dunce and Dumber (otherwise known as Ron Weasley, or sometimes, Ronniekins) so badly they tried to break into the Third Floor corridor to get away.

All it took was a few careful hints to Filch, and he watched with his most unpleasant smile as they were threatened with some classic punishments he rather regretted had been done away with quite a while ago. Filch had just reached some of the more… interesting methods of interrogation when Quirrel passed by and earned Snape's undying enmity by saving them.

And this was only the first few hours. He had seven long, long years to implement all the fine arts of torture he'd perfected.

His cheerful mood was ruined by breakfast – he arrived in time to witness Harry Potter bring yet another first to Hogwarts halls: a Howler, on his very first day, before he even got his timetable.

As he listened to James Potter's magnified voice berate his son for the terrible crime of being Sorted into the right house for him – he didn't know whether to be pleased for Harry that his father remembered he was alive or insulted on behalf of his student and house – he decided that perhaps he could find just that little more contempt for Dunce that would enable him to use his more sinister ideas without receiving a visit from his estranged conscience. It would however, still take until his first lesson with Dunce on Friday before he could initiate Dunce into what the rest of his school years would be – persecution of the highest quality available in schools.

Until then – Snape smirked darkly as he swept past Dunce in the entrance hall with a silent incantation of levicorpus – he could always hire Peeves.

Friday dawned. Snape waited calmly in his dungeons, watching his Slytherins – having been warned by older students that he expected the best of his students, the better to show up the Gryffindors, they were early. Potter – his Potter – he was pleased to note, was flicking through Magical Drafts and Potions carefully. He, like the other Slytherin first years, had been informed of Snape's customary Gryffindor baiting pop quiz, but seemed to doubt the snake on his robes was enough to counteract Snape's legendary hatred of the Potter name. Very wise of him. Snape found himself nodding approvingly, before fixing a scowl on his face and waited for Dunce to be late (again, Peeves, the promise of a new batch of experimental dung bombs, and careful orders to the Bloody Baron to keep away other ghosts who might help them had provided good results).

As they burst into the room gasping – he later heard from Peeves they had been chased all over the fourth floor, a fact he verified by the portraits before adding several ink bottles to his standard bag of dung bombs – he began at once, taking points for lateness.

First blood drawn, he continued with the standard spiel he gave all Slytherin-Gryffindor first year classes, watching Dunce carefully out of the corner of his eye. "Potter," he snapped as soon as the redhead exchanged dire looks with Weasley, and scowled in further annoyance when both looked at him sharply. "This is going to become supremely irritating, isn't it?" He turned and glared accusingly at the black-haired Potter under his care, as if it were a personal insult he happened to be a twin. "Why couldn't you have had the decency to strangle him–" an irritable jerk of the head toward the Gryffindor side of the room was sufficient to inform all present of the 'him' being referred to, "with his own umbilical cord in the womb?"

"Who would you take your vitriol out on then, sir?" Potter – Harry, no, Potter… goddamn the quirk of biology that had resulted in Lily bearing fraternal twins, and especially for bearing them both to term! – inquired in as respectful a tone as could be managed when subtly insulting your teacher.

The entire class held its breath. It was an unspoken rule that you never mentioned Snape's hatred of Potters, Weasleys, Gryffindors… generally, anyone not of Slytherin. Snape stared, and smiled slowly (it would be petty to find pleasure in the whimper this elicited from Neville Longbottom. But then, Snape had often been accused of being petty). Yes, there was definitely potential here. "Hmm. Gryffindor Potter will henceforth be addressed to as the Dunce Who Lived–" cue sycophantic sniggering from the Slytherin half of the dungeon, and to hell with professional integrity, this was war, "and you will have the dubious pleasure of being simply 'Potter'. Unless of course, it is blatantly obvious which of you is on the receiving end of my ire. Is this acceptable?"

He waited a moment for one of the self-preservation-challenged to mutter the inevitable, 'as if we're going to argue with you.'

"Detention, Weasley." He said silkily, gliding back into the half of the dungeon he'd spelled to be five degrees cooler than the rest every time he had a class with the lions. "So, can fame make up for deficiencies of nature? Potter, what would I get if I added powdered root of asphodel to an infusion of wormwood?"

Dunce reddened – Snape felt the brief urge to see if crushing him would result in tomato sauce and quashed it ruthlessly as going against Dumbledore's unspoken limitations upon his reign of terror. It seemed his humiliation threshold was lower than anticipated if he was already turning red – a few more questions and he would be unable to protest at the unfairness, and then points could be legitimately taken for backchat. "I don't know, sir." He said sullenly. Snape smirked. While Dunce might resemble Lily most, none of her intelligence, particularly her talent with potions, seemed to have been passed on. Good. He need only endure five years then.

"Where would I look for a bezoar?"

The expression on Dunce's screwed up face was almost painful. Thinking, it seemed, was terribly hard work. "I don't know, sir." He repeated, each word slightly stressed, as if Snape should pay attention to what was being said.

"What is the difference between wolfsbane and monkshood?"

"I don't know! Okay? Satisfied?"

"Five points from Gryffindor for the terrible combination of idiocy and cheek, Potter." A pause as a thought occurred to him. "You have been taught to read, I hope?" He wouldn't put it past Potter to avoid teaching his son basic literacy skills by claiming his perfect, Dark Lord-vanquishing son didn't need to spend time on such mundane occupations.

"Of course!" Dunce snapped, looking for all the world as if he were insulted. Fancy that.

"Really? Then why have you not read your course books? The answers are there, I assure you." Snape knew just enough about siblings and the possible detrimental effect that favouring one over the other could have on the favoured child's lifespan and quality of life, and so tactfully didn't mention Harry had probably read his course books back to front by now – the potions ones, at least, given the warning older students had given him. He did want the child to live, and be fairly happy living at Hogwarts – or as happy as a Potter in Slytherin with still-living Gryffindor parents could be in any case – otherwise Snape could expect his own life expectancy to match something akin to a mayfly's. He sighed. "For your information, Potter, though hopefully not for the rest of your unfortunate classmates, asphodel and wormwood make a sleeping potion so powerful it is known as the Draught of Living Death." If only House Elves weren't completely immune to bribery, he would have loved to see what would happen if he managed to feed that to Dunce. "A bezoar is a stone from the stomach of a goat that will save you from most poisons–" …oh, dear god, he'd just given him the means to avoid a painful death of mostly untraceable means "– and there is no difference between wolfsbane and monkshood, seeing as they are the same plant, also known as aconite."

The class did not improve, although he was pleased to see Harry was proficient in potions, perhaps even as gifted as Lily.

By the time Longbottom managed to somehow melt his cauldron, a feat Snape had thought beyond even him, Snape himself was near melting point. Having the Dunce Who Lived in his class was fast becoming an endurance test he wasn't sure he had the inner resources of spite to retaliate upon. Just how was it possible without violating all laws of magic and nature known to man for a being even more annoying than both Weasley twins put together to exist? And to manage to be so annoying while ostensibly doing nothing wrong? It was unfathomable, simply unfathomable.

Taking points alleviated the irritation a little, and sending Potter to escort Longbottom to the Hospital Wing did at least get him out of sight (he sincerely doubted the latter would return this period, whatever Madam Pomfrey might say, and if Potter wanted to live to see the end of his first week, he'd take note of Longbottom's evasion). Poor Longbottom. If only the Sorting Hat had gone with its first instinct and put him in Hufflepuff where he so clearly belonged, Snape wouldn't have to despise him on principle – as a Gryffindor of terrifying ineptitude it was expected of him to systematically decimate Longbottom's confidence potions lesson by potions lesson.

If Longbottom had been a Hufflepuff, the much vaunted loyalty of the House would have successfully buoyed him enough to perhaps clue him in to the fact that Herbology was closely related to the art of potion-making, and furthermore allow Snape to be a little more flexible on the matter of his pitiful class work. After all, he had nothing against Hufflepuffs – hard work was a virtue applicable to all areas, whereas bravery was about as relevant to schoolwork as live manticores were to health care.

But as things stood… Merlin's fluffy white beard, Longbottom, a Weasley and the Dunce, all in one class? It was going to be a miracle if he survived the next five years with sanity intact. He was probably going to end up rejoining the Dark Lord in a fit of madness. Or worse, agreeing to spy on him again.

"Potter," he said calmly at the end of the class, "Stay a moment."

Probably entertaining vague ideas of detention, disembowelment or other forms of persecution that would certainly have been his were he his brother, the boy stopped.

It occurred to Snape as he stared into the carefully blank green eyes of Lily's son that all his years as a teacher and spy had hardly prepared him to connect with, train, mentor or otherwise enhance the survival options of the saviour of the wizarding world. These occupations had in fact made him so bitter it was a source of ongoing friendly contention between Pomona and the normally intelligent Filius as to whether he really could curdle milk just by looking at it. Don't think he hadn't noticed them trying to subtly shift pitchers of the white stuff into his line of vision at breakfast each morning.

"I trust, Potter, you have been comfortable in Slytherin? Or as close an approximation as is possible, given your circumstances?"

Harry Potter was a remarkably bitter little boy, if that twist of the mouth was indicative of anything. "Circumstances? Do you mean having Gryffindor parents, one of whom is muggleborn? Or being related to the Boy Who Lived?"

Snape decided, Slytherin instincts be damned, to be honest. "I was actually hoping to lead around to the issue of your brother not, in fact, being the Boy Who Lived, but we can continue with this amusing, if inconsequential line of thought if you desire."

Harry stared for a long moment. Then Snape was the recipient of a smile so cold it could have kept ice cream from melting in a blast furnace. Something in Snape recognised it and started kissing robe hem. He crushed the urge viciously and smirked back.

This was going to be more interesting then he'd anticipated. He might even end up liking the boy, instead of the mixture of resentment and constant exasperation he originally anticipated would be the result of his decision.

He surveyed his new pet project for a long moment. Was he prepared to be teacher, mentor, protector, friend (he was hoping this was avoidable, but if he wanted the boy to trust him it might become necessary) and – damn James Potter for not being capable of fulfilling this vital role in the first place – parent to this boy?

If it drove James Potter to drink/death/damnation/ruination of life and sanity?

Hell yes.