I don't own Harry Potter or anything I allude to.
Cat and Mouse
"...which is why this exception to Gamp's Law of Elemental Transfiguration still holds. Now, can anyone tell me-"
Shrill screams of terror and the grating of wooden chairs scraping against stone interrupted Professor McGonagall's morning lesson. She slowly turned around and was greeted by the sight of dozens of sixth years cowering on top of their desks. She groaned, already knowing there was only one person who could cause a distraction of such magnitude. "MISTER POTTER!" she thundered dangerously, "Detention!"
James Potter looked up at her innocently, a transfigured mouse still ensnared in his hair. "Of course, Professor," he said with a cheeky grin.
Hours later, another angry bellow cut through the muggy afternoon air. "MISTER POTTER!" Professor McGonagall's voice floated down into the schoolyard. Outside, in Professor Kettleburn's classroom, James Potter's quiet snigger was cut short by a yelp when his bowtruckle, seeing its chance, latched onto his finger with its sharp fingers and refused to let go.
James Potter rapped his knuckles on the solid oaken door of the transfiguration classroom. He cocked his head, wondering what the scrabbling noise on the other side of the door was.
"Come in," called Professor McGonagall.
The Gryffindor chaser tentatively cracked open the door. Nearly a dozen mice poured through the gap and into the hallway, causing him to jerk in surprise. He quickly entered the room and slammed the door shut behind him before any more could escape. As he surveyed the classroom his eyes slowly widened in shock and then glee. The stone floor was covered in swarming brown and gray fur and the high pitched squeaking of the animals had reached the levels of a dull roar. A quiet cough caught his attention. He looked up to the top of the office stairs where his teacher stood, arms crossed.
"I am extremely impressed with your talent in runes, Mister Potter," Professor McGonagall's stern face was not as stony as had been expected, "It was an excellent application of runic adaptation to live-animal transfiguration. I am going to recommend to your teacher that you skip a level in your runes class. Your NEWT-level demonstration of your abilities would be better served in a more difficult class where you have less time to create frivolous pranks. I have decided to give you a more lenient punishment. First you will capture every single mouse and place them in that cage," she gestured at a large wired pen at the center of the classroom, "then you will transform the mice back into snails. Once you have completed those two tasks, you are free to go."
A wide smirk split the prankster's face and he reached for his wand. He froze when Professor McGonagall's voice again rang out. "No magic until all the mice have been secured, Mister Potter." The slam of her office door punctuated her words.
Muttering darkly and shaking his head, James stowed his wand and set about his task of capturing transfigured mice.
Several hours later, Professor McGonagall poked her head out of her office window and smiled at the humorous sight of the frazzled boy chasing madly after mice. She aimed carefully at the cage that never seemed to reach past half full and flicked her wand. A mouse disappeared. She retreated back into her office rubbing her hands together and cackling quietly to herself. Down in the classroom, a mouse poofed into existence under a desk in the corner. It squeaked confusedly, whipping its head around several times to regain its bearings, and then silently rejoined the mob of mice.