A Marauders Riddle

Trasfiguration

In Transfiguration

Tris loved attention. When everyone had turned to look at her and the Marauders when they walked into breakfast, she'd felt so powerful and confident. As she strutted into Transfiguration by Sirius' side, she felt eyes on her. She could almost taste the envy in the air and it made her brave. She leaned over and kissed Sirius on the cheek. There were gasps, poison-filled whispers, even a few sobs from some lovesick girl's who clearly didn't have a chance with Sirius. With what Tris owned. Tris's pulled away and smiled gently at Sirius. He blinked, looking shocked for a minute, then broke into a beaming grin. He took her hand and pulled her to a desk at the back. The class started finding seats with friends, racing each other to desks at the back. Everyone had just about settled when the door opened and McGonagall walked in.
"There was no need for that rush to seats," McGonagall said reprovingly, "because in this class this year, there is going to be a seating plan. All of you take your bags and stand against the far wall."
With much moaning and complaining, the class did as they were told.
"But Minnie," Sirius whined, "why this year?"
McGonagall pursed her lips, her whole face pinched in disapproval.
"Because, Mr Black," she said icily, "this year is your OWL year so you can't be messing around with your friends in lessons. And my name is Professor McGonagall and I would appreciate you calling me as such."
Sirius subsided, still grumpy. Tris put a hand on his arm and smiled sadly.

With Poppy

"Sirius Black, over there with Bellatrix Black," McGonagall said.
Both Sirius and Bellatrix let out load groans and glared in the other's direction.
"But Professor," Bellatrix cried, "can't I sit next to Poppy? She's new and I can help her."
McGonagall shook her head firmly and pointed to the desk she'd indicated before.
"Poppy Riddle, the desk in front of the Blacks with Lily Evans." McGonagall said.
Poppy kept her expression neutral in front of her classmates, but inwardly she was smiling. Lily followed her to the desk and they both sat down. Poppy watched the line of students dwindle until there were only four left. One of them was Lucy Abbot, one was Charlie, one was Tris, and the last was a Slytherin boy Poppy didn't know the name of.
"Lucy Abbot and Andrew Parkinson," McGonagall said.
Lucy and the Slytherin boy walked to one of the two desks right at the front of the room. Lily giggled and nudged Poppy.
"Tris is going to have a bad time of it with Charlie next to her." Lily murmured.
Poppy nodded in agreement. She loved her half-sister but sometimes it was only the family ties that kept their friendship from collapsing. Now was one of those times.
"Charlie Fawkes and Trissa Riddle." McGonagall finished.
Giggles swept the room as Tris and Charlie gave each other disgusted looks and reluctantly moved towards the last desk.
"Now that that is sorted out," McGonagall started. The class fell silent. "We have three Animagi among us today. Animagi are using a form of Transfiguration when they transform. This will be shown now when I and Trissa and Poppy Riddle transform."
Whispers among the class. Poppy and Tris got up from their seats and moved towards the front of the room, Poppy reluctantly and Tris eagerly.
"One, two, three," McGonagall whispered.
On three, the three changed into their Animagus forms. Tris shrank, growing fur and a tail and pointy ears, as did McGonagall, until two cats stood on McGonagall's desk. One (Tris) was a tonkinese cat and the other (McGonagall) was a tabby. At the same time, Poppy grew upwards. She grew wings and a tail and her bones became very defined, until a Thestral stood before the class. It was like a Thestral in every way, apart from the fact that Poppy's Animagus form was not invisible to the majority of people. People oohed and aahed over the cats and the magnificent Thestral. McGonagall made a flicking motion with her tail and the three turned back into humans. The class started clapping and Poppy and Tris bowed, not sure what else to do. From outside, Poppy heard the neighing sounds of another Thestral.