7 February 1974
Three days after the glitter prank – Sirius was still picking pink confetti out his gorgeous hair – the Marauders struck back. While the girls joined Remus and Sirius for an animated game of Exploding Snap in the common room one evening, James and Peter "borrowed" their History of Magic textbooks from a nearby table and charmed them to recite dirty limericks whenever one turned a page.
Thus, the following morning: "THERE WAS A YOUNG LAD FROM KENT!" Mary's textbook screamed, before she was able to collect herself and slam it shut. Laughter echoed throughout the classroom, and Remus smirked at his housemates.
"Your move, ladies."
...
With Valentine's Day around the corner, Dorcas suggested lacing a box of chocolates with an extremely potent version of Pepper-Up Potion, which had effects similar to the laughing gas used by Muggle dentists, and gifting them to the Marauders as a fake peace offering. But Lily and Mary weren't comfortable with the idea of drugging the boys against their will – even if the effects of the potion were likely to be pleasant – so it was back to the drawing board.
After a few nights of brainstorming, they settled on a relatively harmless trick from Mary's summer camp days. While James and Sirius were at Quidditch practice one afternoon and Remus and Peter were hanging around to watch them, the girls snuck into the boys' dormitory and refilled their shampoo bottles with temporary Muggle hair dye.
The next morning at breakfast, James' curly bush of hair had a distinct red tint to it, and Remus and Peter's normally lighter-colored hair was now fully blue. And while Sirius was initially the most upset by this prank – he took a lot of pride in his hair, after all – after about half a day it became clear that his new purple highlights looked great on him.
"Maybe we should've drugged them, after all," Mary grumbled over dinner, as Sirius preened and a fifth-year Hufflepuff girl stopped by to compliment the Marauders on their new looks ("Very punk rock!").
"No," Lily said, giggling at her grumpy friend, "We're just not thinking big enough. Our next move has to be brilliant."
As if he'd heard her, James glanced at Lily and grinned. "Is that all you've got, Evans?" he called from the other end of the Gryffindor table. "If so, maybe you should go ahead and admit defeat."
"Never!" Lily yelled back, green eyes shining with determination.
Dorcas lifted her chin defiantly at her friend's proclamation and added, "We're just getting started."
"Good." James tipped his pumpkin juice in their direction with a satisfied nod. "Cheers to a bit of healthy gamesmanship, then."
"Or gameswomanship," Mary corrected, raising an eyebrow. "Because we're going to beat the pants off you."