Disclaimer: I do not own Harry Potter or DC/Vertigo. I'm just borrowing them for a bit. (Though I wouldn't mind working out a short-term lease on John, if you're offering.)

The Laughing Professor

A Harry Potter/Hellblazer crossover.

oOo

Harry drummed his fingers idly on the wooden table top, his eyes roaming over the Great Hall as the first years were sorted. Scanning the Head Table, he leaned over and whispered to his friends, "There's no DADA teacher."

Hermione looked annoyed that Harry was talking but she soon frowned, realizing that he was right.

"You don't think they gave it to Snape, do you?" Ron's voice held just a hint of panic. Beside him Neville went white and, for a moment, it looked as though he might cry.

Hermione merely looked thoughtful. "I don't think so. Someone would have to take his place in Potions and I don't see any new faces." Both Neville and Ron seemed to relax at that. "Now, be quiet and watch the Sorting." She pointedly turned her back on them and focused on Daniel Gardiner, the soon to be Hufflepuff.

Harry rolled his eyes and continued drumming on the table, daydreaming about turning Snape into a house elf. A house elf named Sevvie. The mental image of a jaundiced elf with yellow teeth, a long crooked nose, an evil sneer, and a black pillowcase was too much and Harry had to slap a hand over his mouth to contain his laughter. His snickers soon turned into a pained grunt when Hermione elbowed him in the side, gesturing emphatically at the headmaster. He listened half-heartedly to Dumbledore's opening speech, only perking up when he heard mention of the defense class.

"I'm sure some of you have noticed that our new Defense Against the Dark Arts professor is missing. Unfortunately, he was called away last night and is currently investigating a possible nundu sighting in Namibia. Rest assured, he will be back in time for class tomorrow morning." A few students groaned. "Now, tuck in."

Harry frowned as he picked at his roast beef. Something about Dumbledore's speech seemed…off. Why was a DADA professor looking for a nundu? Wouldn't a task like that be better left to a specialist on magical creatures? Also, although the headmaster was smiling, there was a tightness to his smile, visible only at the corners of his mouth, and his eyes weren't twinkling.

A non-twinkling Dumbledore? The very thought made Harry a bit uneasy. It just wasn't natural.

Of course, Harry had no way of knowing that the cause of Dumbledore's ill humor was currently in the DADA professor's chambers, passed out drunk and snoring loudly enough to rival even a dragon's mighty roar.

oOo

The sixth years had a double period of NEWT Defense Against the Dark Arts first thing Monday morning. Though a few students were still bleary-eyed with sleep, all were eager to meet their new professor. Of course, many simply wanted to see what kind of crackpot Dumbledore had hired this year, but they were eager nonetheless.

The trio settled at a table near the front of the classroom, turning a critical eye to the room around them. The large professor's desk, battered students' tables, and blackboard remained unchanged from last term. Otherwise, the only decorations in the room were a series of odd runes drawn on the floor, ceiling, and walls. There were no books, no supplies—nothing. The room smelled a bit off, too. Harry swore that the stale scent was familiar, but couldn't quite place it.

Needless to say, Harry was a bit skeptical of the new guy's prowess in defense.

The bell sounded and he turned his attention to the door, waiting expectantly for the mysterious new professor.

Fifteen minutes later, Harry was still waiting.

The class was starting to get restless. Seamus, Hogwarts' resident bookie, had his black book out and was taking wagers on the absent instructor. Harry closed his eyes and rubbed the bridge of his nose, trying not to notice that Ron was slipping Seamus a galleon for 'DADA professor is an inept git' and seven sickles for 'Harry runs yet another DADA professor off.'

"Seamus?"

The sandy-haired Irishman stared at Harry, his deer-in-the-headlights look saying quite clearly that he knew he'd been caught.

"What are the odds on me running him off?"

"Um…two to one."

"And on him ending up in St. Mungo's?"

"Five to one."

Harry nodded, then reached into his robes and produced his money pouch. Sliding five shiny golden coins across the table, he smirked. "Right. Put five galleons on St. Mungo's."

Incensed, Hermione sat stiffly upright, ready to unleash a lecture on respecting professors and gambling when the door slammed open. The resultant boom echoed through the stone room, immediately returning everyone's attention to the front of the class and the man that was now standing in the doorway.

"Ah, fuckin' hell, that's loud."

The man leaned one arm against the wall, the other rubbing circles on his temple, obviously in pain. Slowly, he made his way across the front of the classroom before collapsing in the chair behind his desk. He squinted at the windows, flicking his wrist and conjuring curtains for half of them.

He still hadn't looked at the students.

They, on the other hand, were staring in shock. The man didn't look like a professor. He didn't even look like a wizard. His short blond hair stuck up all over his head, as though he'd just rolled out of bed. And judging by the redness of his half-closed eyes, that probably wasn't far from the truth. He was dressed like a muggle in black slacks, a white dress shirt, and a skinny black tie. Over it all was a rumpled tan trench coat, stained and worn threadbare in several places like a veteran auror's battlerobes.

Harry watched, almost mesmerized by the spectacle, as the man produced a packet of cigarettes from his coat pocket and lit one. Well, at least that explained the familiar smell.

The rumpled professor took a long drag and sighed, the exhaled smoke curling sinuously around his head. "That's better."

A thud next to Harry caused him to drag his eyes away from the front of the room and to Hermione, whose forehead had impacted with the tabletop. For a moment he thought she was crying, but soon realized that it was laughter, albeit of a slightly crazed nature.

"I can't believe this! Our professor—the man responsible for teaching us how to survive against Voldemort and the Death Eaters—IS HUNGOVER!"

As for Harry, it hadn't escaped his notice that the man had conjured the curtains without using a wand, and that even now he was surreptitiously studying the students. As the stranger tapped some ashes on the stone floor, Harry leaned backwards and whispered to Seamus. "Cancel that last bet."

"You sure? Seems like galleons in the bank to me."

"Nah—I've got a good feeling about this guy."

Seamus looked at him like he was crazy, but returned the money.

Harry dropped the coins in his pocket and looked up, only to find himself locking gazes with the man's pale blue eyes. Though they were bloodshot, his stare was piercing. For a single disquieting moment, Harry felt as though the man were looking into his very soul. Unbelievably, he seemed…amused? That couldn't be right, could it? But no, it was there in his eyes. Definitely amusement. With a barely noticeable smirk, the professor turned his attention back to the class.

"All right, you lot. I'm John Constantine, and I'm here because I owe your esteemed headmaster a favor. Anyone has a problem with that, take it up with him because I don't give a rat's arse."

The students merely watched, wide-eyed and unsure, as he continued.

"Now pay attention, because this is probably the most important thing you'll learn in this class. I'm about to tell you the ultimate secret of magic—and that's that any cunt can do it. Don't let anyone tell you otherwise. The wizarding world has been taken over by a bunch of fuck-ups and arrogant bastards, all positive that their ability to wave a poncy little wand and say a few words makes them Merlin Incarnate and superior to everyone else on this godforsaken planet. Their noses are so far up each other's arses that they're blind to the truth—that any bloke or bird right off the London street can do anything they can do. All it takes is a little bit of knowledge and a whole lot of will, then abracadabra, hocus bloody pocus—you've got magic."

Silence.

Complete and utter silence. Harry was reminded of the old adage "so quiet you can hear a pin drop." He was seriously considering transfiguring his quill and finding out if the saying was true when the shouting started. No surprise, it came from the Slytherin side of the room, where a majority of the hardcore pureblood supremacists seemed to congregate.

Glancing to his left, it seemed like the speech had made an impression on Hermione, too. She studied the man as she would a completely foreign specimen, unsure of how to classify him.

Harry, on the other hand, knew exactly how he felt. Despite his gruff exterior, the man obviously had a lot of knowledge and experience to share. Though it might be a trial to drag it out of him, Harry was willing to try. If you asked him, he couldn't explain how or why, but he knew that this man had been to Hell and back. More than anything, Harry wanted to defeat Voldemort. He had a feeling that before it was all over, this cynical, profanity-spewing, chain-smoking man currently sitting before him and smirking at a room full of gobsmacked students would end up being one of his greatest and most powerful allies.

Harry grinned as he shoved his textbook haphazardly back into his bag, eager to see what the future held for the wizarding world and this strange, laughing professor.

oOo

Author's Note: The "ultimate secret of magic line" is actually a part of the Hellblazer canon, but it fit the scene so perfectly that I had to borrow it.

Also, a big "thank you" to my amazing beta Jaki.

Thanks for reading. Constructive criticism is appreciated.