Disclaimer: I don't own anything you see here, so I can't accept any money for it.
The students sat in the Defense Against the Dark Arts classroom, awaiting their teacher. The last time they were forced to wait like this, Snape had been substituting. They sincerely hoped he wouldn’t be doing so again.
Just then, the door swung open and the tall, curly-haired man made his way to the front of the room, long scarf flying behind him. On the chalkboard, he wrote The Doctor in big letters. He turned around and greeted them cheerfully.
“Good afternoon, class, I’m your new Defense Against the Dark Arts teacher. You may call me the Doctor,” he said.
“Doctor,” said Draco disdainfully. “Isn’t that a Muggle title?”
Ignoring him, the Doctor continued his lecture. “While I am not a wizard per se, I can do the same things you can do, except I use just my mind. Your Headmaster feels it is time to teach you to do the same, since each and every one of you has that power.”
“You’re a Muggle?” exclaimed Ron.
“Not exactly,” answered the new teacher. “Now what was I saying...yes. You wizards have come to rely on your wands so much that you haven’t fully developed your natural magical ability. The wand is essentially a physical and psychological crutch, and dependence upon it can become quite the inconvenience, especially in a situation where you don’t happen to have it. Now, Time Lords like me…”
“Wait a minute,” cried Ron. “Time Lords?”
The whole class looked dumbfounded.
“Yes,” the Doctor answered brightly, eyes round as saucers. “From Gallifrey.”
“You mean to say,” asked Hermione, “you’re not from Earth?”
“Well, not everyone is,” answered the Doctor, shrugging.
“I knew there was life on other planets!” Luna exclaimed. “I told people there were beings from other planets walking around. Somebody wrote an article about them in my father’s magazine.”
People turned to stare.
“What’s Luna doing here?” hissed Ron.
“She was in Harry’s DA class last year,so she scored high on her OWL," Hermione whispered in reply. “Be quiet.”
Ron looked around. Such a small number of students had achieved scores high enough to take Defense Against the Dark Arts that the school was offering only two time slots for the subject: one for the sixth years and one for the seventh. He noticed that most of the class that wasn't Slytherin was composed of Harry's former DA students.
“And you would be right,” the Doctor was saying, smiling.
“Wait a minute,” said Hermione, dubious. “The odds against intelligent life from other planets even MAKING it to Earth are…”
“Several billion to one against,” said the Doctor, nodding. “Unless you factor in travel through time and space.”
“I told people there were beings who could master both time and space at the same time,” said Luna triumphantly.
With a huge grin, the Doctor said, “You are quite a perspicacious young lady!”
Luna smiled dreamily.
“And Time Lords can do magic with just their minds?” asked Harry.
“Not really magic,” answered the Doctor. “It’s actually psychic manipulation of the physical world. That is essentially what magic is. That’s not to say that Gallifreyans don’t use crutches of their own. This is one of my personal favorites,” he said, pulling out a long, thin object with a light in the side of the top. "It’s called a Sonic Screwdriver, and it works like this.”
The screwdriver emitted a red light that filled the room. Draco’s wand went flying from where he had concealed it under his desk, poised to hex the Gallifreyan. Draco suddenly looked nervous. There were sounds of awe. The respect-level in the room for this new teacher rose dramatically.
“But-how?” spluttered Ron.
“But electronics don’t work at Hogwarts,” said Hermione.
“Right you are,” said the Doctor. “But this isn’t electronic. It’s Gallifreyan technology. ”
“Bloody hell,” whispered Ron.