author's note: I know students from all four Houses don't normally have classes together. But Harry Potter is so popular that all the students want to hear him, so they're having several bigger classes on the day he visits as a guest lecturer. By the way, Daniel Smith is my invention, but he's meant to be the son of Zacharias Smith, a Hufflepuff who appears briefly in "Order of the Phoenix."

As usual, I don't own the Potterverse or much of anything in it, and I wrote this piece solely for entertainment purposes. Not intended to diagnose, treat or cure any disease. Not even fanfiction addiction.

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"Will you tell us about the battle in the graveyard when you were a fourth year, Professor Potter?"

"No, I want to hear about the Chamber of Secrets!"

"Please, tell us the story about how you stole the egg from the dragon—"

"Slow down! Slow down!" Harry held up his hands, laughing. "I came in today to teach you about Defense Against the Dark Arts, not to tell stories. Anyways, what you've heard about me is probably exaggerated."

"No, it's not!" piped a Hufflepuff second year. "My mother was there at the Battle of Hogwarts, she told me all about it!"

Harry looked at her. "Your mother's Hannah Abbot, isn't she?"

"Yes, sir!" said the blond girl, delighted. "My name's Alison!"

"Charmed," said Harry, nodding. "Well, the Headmistress asked me to talk to you all about the Disarming charm, Expelliarmus. That, you may've heard, is a spell I use a lot --"

"Yes, you killed You-Know-Who with it—"

"His name's Voldemort, and I didn't kill him with it," corrected Harry, patiently. "Like I said, it's a disarming spell. All it does is make your wand fly out of your hand. When I tried to use it on Voldemort, that was a bit of a special circumstance –"

"His own spell bounced back and nailed him!" broke in a Gryffindor boy. "I read it in the updated Rise and Fall of the Dark Arts..."

Harry ran his hand through his untidy black hair, which was beginning to show a little silver above the ears. "Look, who's teaching this class? It seems like you lot already know everything."

The class settled down. "Sorry, Professor." "Sorry." "Go on, teach us your lesson, we'll be quiet."

"Thank you," said Harry. "Now, the Disarming Charm, like I said, is mainly useful for making your opponent's wand fly out of his hand. It goes up in the air toward the person who cast the spell, so if your reflexes are good, you can catch the other wizard's wand. Then you've got two wands and he hasn't got any, so he's pretty helpless. Or she, of course," he added.

"It's possible to do a little magic without a wand, so you can't let your guard down even then, but most wizards never bother learning how, so you're a lot safer if your enemy is wandless."

"How can you do magic without a wand?" asked a brunette Ravenclaw.

"That'll have to wait for another lesson," said Harry. "Sorry, but it'd take a while to explain. Ask Professor Flitwick, he could probably tell you. The bottom line is, you've all done a few unintentional spells before, when you were kids, some of you even before you found out you were wizards and witches, right?" All the students nodded.

"Well, then," said Harry. "I did, too. I remember one time, I turned my teacher's wig blue ..." He smiled briefly and did not finish. "Well, anyways. The wand is just a tool, the magic comes from you."

"But what about that ... Reverse Spell Effect thing ... I'm sure I read about –" began the Ravenclaw girl.

"Yes, you probably did," said Harry, with a small sigh. He was strongly reminded of Hermione when she was a first year, only that Ravenclaw student facing him had neater, straighter hair.

"Wands can do funny things sometimes. They don't exactly have minds of their own, but their cores come from living creatures, you know. Unicorn hair, dragon heartstring –" He held up his own wand. "—and phoenix feather. Things like that. I think even wandmakers don't always know exactly how a magic wand works, but it's true they occasionally do things their owners weren't expecting.

"But that's another lesson for later. It usually doesn't happen unless the two wands are alike in some special way, like if they both have a feather from the same phoenix, and that's rare, so you don't need to worry about it. Right now, I want you all to divide up in pairs so you can practice Disarming each other.

"Wait, let me demonstrate first – can I have a volunteer, please?"

Everybody in the classroom began shouting, waving their hands and bouncing in their seats.

"How about you, there, in the corner," said Harry, pointing at a shy-looking boy with pale hair. "What's your name?"

"Daniel Smith," said the boy, "and I'm in Slytherin." He didn't speak very loud, but his eyes dared the teacher to comment.

Harry pretended not to notice. "Okay, c'mon up here then, Smith," he said. Daniel had no choice but to walk to the front of the classroom.

Several students were watching him with hostile expressions. Slytherins were not very popular in recent years, despite the role Professor Snape had played in defeating Voldemort. All the students knew Snape had also murdered Professor Dumbledore, who had been a much better headmaster. And, as everybody knew, You-Know-Who and his Death Eaters had been Slytherins too. Harry was already aware of all this, but he didn't like the looks the other students were giving this boy.

Daniel Smith stood there with his wand in his hand, looking sullen. He knew he was about to be Disarmed and made to look like a fool in front of everyone. But Harry was a step ahead of him.

"Is everyone watching?" Harry called out. "Great. Smith here is going to demonstrate the Disarming Charm ... on me."

Daniel's head snapped up. He looked completely surprised. The class murmured, "ooohhhh..." Potter just grinned and turned to face the boy.

"You remember the incantation, right? It's 'Expelliarmus!' Whenever you're ready."

Daniel pulled back his sleeves a little, pointed his wand at Harry, and said loudly: "Expelliarmus!" Right on cue, there was a flash of red light and Harry's wand flew out of his hand – and Daniel reached up and caught it, perfectly.

The class broke into applause. In spite of themselves, they were impressed. "Great job, Smith!" said Harry warmly, holding out his hand for his wand. "Did you all see that? He got it exactly right the first time!

"Now, all of you come into the middle of the floor here, divide up in pairs, and we'll practice Disarming each other." As soon as everybody had gotten up from their desks, Harry flicked his wand and the desks scooted back against the wall, creating a space in the center of the classroom.

Daniel smiled, and his cheeks turned a little pink. Harry got the impression the boy didn't smile that often.