They waited until the between classes stampede ended before going in. The main hallway was as expected, open and bare, save the rows and rows of lockers. The Doctor couldn't help but smirk. The style, level of technology, and aesthetics may be different, but the overall basics weren't entirely different from the Academy on Gallopfrey. It was enough to bring up a number of rather pleasant memories. He did notice that the same wasn't true for Derpy. She was obviously uncomfortable, biting her lip and glancing around.
"C'mon, Derpy," the Doctor said in as soothing a voice as he could muster. "You've been less nervous about sneaking into Dalek motherships."
Derpy smiled weakly. "I know, I know. I'm usually better than this."
"Was it really that bad?"
Derpy sighed. "Not all the time. You know how Ponyville is. Friendliest place in Equestria and all that. But it really only takes one bully to really ruin your day. Or week. Or year. And y'know, even the nice ponies treated me just a little different. And that's okay. I am just a little different. I'm proud of it, even. At least, nowadays. But still..."
"You don't have to do this, you know."
Derpy laughed. "You can't do anything without me, and you know it."
The Doctor scoffed. "I survived for centuries before you were born, you know."
"Sure, sure. Alone, though?"
The Doctor opened his mouth to reply, but nothing came out, so he decided to close it again. Derpy laughed again.
"What are you doing in my school?" a sudden voice interrupted, causing the two to jump. They spun to see a tall woman in a classy pantsuit strolling down the hall with a cross look on her face. The Doctor and Derpy instantly recognized her, given the multi-colored hair that still managed to look like a mystical cloud, despite not actually flowing like one.
The woman, the local version of Celestia, stopped a few feet in front of the intruders, hands on her hips, and a stern look directed specifically at Derpy. "Miss Derpy? What are you doing out of class? And who is this?"
Derpy fidgeted under the scrutiny. "Errr, well, uh..."
"Hello, yes, sorry, hi. I stumbled upon this young one as she was coming out of the loo, and she was just showing me where I needed to go," the Doctor interrupted with a smile as he withdrew an old wallet from his coat pocket. "My credentials." He opened the wallet and showed her the blank paper within.
After just a moment of looking the paper over, Celestia's demeanor softened. "Well, you certainly came fast," she said with a smile. "I was certain I'd have to teach the next class myself."
Derpy looked confused. "The next class...?"
Celestia turned her gaze back down on Derpy, this time much softer. "I apologize. Mrs. Cheerilee suddenly had to go home. Stomach ache. Left us in a bit of a bind. I wasn't certain if we'd be able to get a substitute at all today, let alone this quickly." Turning her attention back to the Doctor, she added, "If it's all right with you, Mr. Turner, I'll show you the rest of the way."
The Doctor nodded. "If it's all right with you, I'd like to thank Miss... er... Derpy, was it?... real quick before we get going."
Celestia nodded. "Certainly. Be quick, you both need to get to class."
The Doctor turned his back on Celestia to see Derpy grinning up at him. "Did you just psychic paper Princess Celestia?" she whispered.
"I think it's Headmistress Celestia, but yes, I did," he whispered back. He pulled out his sonic screwdriver and handed it to Derpy. "Here, I set it to beep at you like a metal detector. Not as precise as the readings I can see, but good enough. I'll get back to you as soon as I'm done with the class."
Derpy pocketed the sonic then ran off in a direction she hoped would be towards the classrooms. "Bye Principal Celestia!"
"No running!" Celestia called back. She rolled her eyes, though the Doctor did notice a very subtle smirk of amusement. "Now, Mr. Turner, if you'll follow me, I'll take you to your classroom."
The Doctor gave Principal Celestia an exaggerated bow. "Of course, my lady." As the two began walking down a hallway opposite of the one Derpy took, he said, "Now, as you might imagine, I was called over in something of a rush, so, if you don't mind my asking, what class am I set to teach?"
"Physics."
The Doctor rolled his eyes. "Physics. Of course."
~DrW~
"Sorry! Sorrysorrysorrysorry," Derpy apologized as she stumbled out of the boy's room. "I really didn't mean to."
"Yeah, no problem, Derpy," a voice from within said in the tone of one who was used to it.
Derpy sighed and entered the girl's room. She had been so focused on following the beeping sonic that she hadn't been paying attention to where she was going. And there's another me who's just as bumbly as I am. Makes things easier, I guess. The sonic beeped again. "Oh, beepies!" A moment later, she was in the back stall, the sonic beeping particularly loudly when pointed at the drain on the floor.
"Kreeee!" The sudden sound from within the drain made her jump. She heard a distinct scratching sound that faded quickly as the sonic stopped beeping. Derpy groaned. "The sewers. It's always the sewers."
She turned to leave, only to come face to face with... herself. At least, she assumed it was herself. Grey skin, blonde hair, blue and green outfit, and googly eyes. A second later, she also confirmed that she wasn't looking at a mirror. A nervous smirk crossed her face. "Hi," she said with a small wave.
The other Derpy suddenly sprouted a huge smile and said, "Hi! You from the other side of the portal thing?"
"I'm... wait, what?"
~DrW~
"Hello there, class," the Doctor said as he entered the classroom. "As you might guess, I'm your substitute teacher for the day. I'm Mr. Time Turner." Here he wrote his name in big letters on the chalkboard. "Now..." He turned to face the class, and as soon as he saw the room full of eyes staring up at him--a certain appreciation in the eyes of roughly half the girls that he did, in fact, catch--his mind froze. Again. "Sooooo... Physics. Physics, physics, physics. Physics."
Dammit.
Though, he did note that a couple of boys really seemed to appreciate that he said that. One of them even pumped his fist. That was odd. "So, let's begin with a rundown of what you already know..."
And the class continued on, running actually rather smoothly. The Doctor actually was quite enjoying himself, truth be told. With any luck, He'd be able to catch up with Derpy after class and she'd have something for him on the Nn'tok, and they'd be in 'n out within an hour. He didn't notice the girl with the fiery red hair in the back that watched him the whole lesson through, a shrewd expression on her face.