Severus Snape entered the crowded great Hall, and looked up at the enchanted ceiling as he made his way to the Slytherin table for some breakfast. Unmistakably, it was a rainy day; the wash of grey clouds above him and droplets of rain pattering on the windows made that clear.
As he found a place amongst the rest of the fourth year Slytherins, Snape felt suddenly light-headed as he saw Lily flash a smile at him from the Gryffindor table. He grinned back, his pulse quickening as she motioned to meet her in the library later for some studying.
Severus started to butter a piece of toast just as the Slytherins around him started whispering heatedly about the Marauders. For Slytherin, they were fatal enemies. The Slytherins had too much from them- toilets backing up, flooding, food poisoning- all were the Marauder's acts of 'fun'. Eating his toast, Severus smirked; he had his own fair share of pranks from the Marauders. But that wasn't why he was smirking. He planned it out very carefully, and took his time over it, the plan with which he would make his avenge to the four insolently immature boys.
At the Gryffindor table, he saw them cheer with laughter as one of the younger students started choking on her breakfast. He didn't normally feel sympathy for Gryffindors, but he couldn't help the fleeting stab of understanding for the girl. He knew all too well what it meant, made fun of as he got hurt- he himself was too often their target.
Severus pointed his wand at the girl, and hoping that nobody got in the way, he whispered,"Anapneo"
The girl stopped gagging immediately, but her face glowed bright red, clearly embarrassed. Severus sighed. If he was going to do something worthwhile, he might as well do it wholly. Again, he pointed his wand over at the Gryffindor table, this time however, at James and Sirius, and muttered another incantation under his breath as he grinned, waiting for the result. "Waddiwasi."
The food James and Sirius were holding sprang up unexpectedly out of their hands, and forced its way into one of their nostrils. The Gryffindor table roared with laughed and cheered at the usually very proud Marauders. Snape smothered his laughter, trying to continue eating as the Slytherins joined in on the glee as well.
After breakfast, Severus went outdoors to search for some ingredients to finish up a Potion he had been busy brewing for these last few days. He had discovered the Potion whilst browsing some books absent-mindedly in the library, and thought it would be perfect for getting his revenge on certain annoying Gryffindors.
Snape inhaled the woodsy, rainy smell around him. He loved the smell. It made him feel free from everything, and helped him clear his mind. He shuffled along the edge of the Forbidden forest, listening idly to the sound of the trees swaying in the wind, as he looked for the small purple plant that would finish up his Potion.
Just as the rain was starting to fall heavier after a few minutes of rest, Severus spotted the purple plant by a tree a bit ahead of him. He quickly cut it out as carefully as he could and pocketed it as he sprinted back towards the castle without stopping. He stopped momentarily at the mouth of the Entrance Hall to catch his breath, and looked back outside. The rain was getting heavier and heavier. Just my luck, I found the plant just in time, he thought as he went down to the dungeons.
A few corridors later, Severus was by a frothing cauldron in an unused classroom down in the dungeaons. Snape read the last line of instructions from the book wide open on beside his cauldron.
Step 13: Add the Blattasero (chopped up) to the frothing Potion, making sure to give the Potion enough time to absorb all the essence possible from the plant.
Severus smirked. The secret of Potions was to know what you're working with well, even though a bit of a nack for it helped as well. Plants like these he was working with, he knew well, were far better crushed. As he finished up the Potion, his pulse quickened as the time to get his revenge got closer.
Once out of the Dungeons, finding the Marauders wasn't that easy. Especially if they were in the common room. However, there was also a possibility that they were in the Library, with Madam Pince breathing up their necks as they made a racket, as always. Deciding to check the library first, Severus took out his wand and did a good Disillusionment Charm on himself, then one on the cooled down Potion, which he placed inside a flask.
Running up a few flight of stairs and passing a few corridors, the Slytherin fourth year finally found himself at the library. He entered cautiously making sure he didn't make a sound a he passed Madam Pince. He strolled a few bookshelves, wide-eyed for the Marauders. Luckily, he spotted them by a window at the back of the Library.
Totally invisible by his excellent charm, Severus flicked the Potion flask open and with his wand, hovered it to where the Marauders sat. Then, slowly, tipped a little of the Potion on each of the Marauders. Having the property of being a very light Potion, they didn't feel it as it smeared on top of their heads. Or at least, that's what Severus assumed he would see, if he hadn't made the Potion transparent to the naked eye.
Not a moment after he was done, the Marauders got up, clearly going down for dinner. All for the best, Severus thought, more people to see the results.
Later down at the Great Hall, Severus laughed with derisive laughter along with many others as the Marauders tripped hastily out of the great hall, their face covered with pus-filled boils, and with their hair turned pink. But the best thing was seeing Sirius' most panicked face as he continually repeated, "My hair… m-my beautiful hair."