"I will not tolerate any missing ingredients, overuse of ingredients, or for that matter, under use or no use at all." Professor Snape drawled, looking pointedly in Potters direction.

Malfoy knew that in potions, he was the master of the class. There was no denying that Snape hated Potter, almost as much as he did. Draco smiled and rose up from his cauldron, and it was here, in Potions that he could extract his revenge. He began to saunter over to the front of the class. To 'speak' to Professor Snape, conveniently passing Neville's table of ingredients.

"Having fun there Neville?" he hissed maliciously
"Uh…uh…um"
"Oh shut up," Draco whispered back impatiently. "I was being sarcastic, but obviously your idiocy doesn't understand what that is either."

"Leave im' alone Draco" came Weasley's voice.

Draco stood tall and grabbed Neville's Monksbane root, smiling nastily. This was exactly what he'd wanted, an excuse to walk past their cauldron and accidentally drop something in it.
"Hello weasel." He said, slowly and deliberately. "Making a mess of your potion as always I see."
"Shut up Malfoy." Granger said.
"Shut up mudblood!" he spat at her viciously, and then composed himself.
"See you up the front Potter." He said winking, and slipped the root into Potter's' cauldron.

The effects were almost immediate, and Draco barely had time to sit down before the potion began to bubble and froth over.

"What's this then? What's going on he….DUCK"
Professor Snape yelled and jumped on the nearest students, crushing them.

The cauldron had exploded, covering them in a sticky purple substance. Nearly all of the Gryffindor students had been covered, as had Professor Snape. A slight glitch in the plan of course, but then, Draco smiled, in between fits of laughter, it would give him even more of an excuse when Potter accused him. Cause honestly, what student in their right mind would put a shrinking potion on their own head of house.
Damn I'm good, he stood from his table, praising himself, I am just so bloody good. All of the Slytherin's had joined in his laughter now, watching as Weasley's' arms shrank, Neville's legs, Potters head, and Grangers body. All of them had some kind of ailment, and were yelling and trying to stand, or trying to hold up their head, which was now too big for their small bodies. Draco made to move out.

"IT WAS MALFOY! He put the extra stuff in there, it was all his fault!" Potter screeched.

"MR…P..O.TT...E..R! I will not tolerate any accusati…. ions in…m…y cla..ss. Fif….Fif….Fity ponts fom gwiffimdore." Professor Snape tried to yell, but the shrinking potion had touched his nose and mouth, which were now so small he seemed to be having difficulty breathing.

Draco turned and watched Potty and his posse' becoming increasingly smaller. He looked at Granger and felt a twinge of… What was that exactly? Regret? Remorse? He shrugged, and shook his head and kept walking, Madam Pomfrey and Dumbledore rushing past them to the students aid. Ahhh who cares he thought. It is only Mudblood after all.