The Gryffindor Common Room, 1989...
Fred and George Weasley sat in front of the common room fire, trying to figure out why Filch would have an innocuous bit of parchment locked up in a drawer labeled dangerous. George pulled out his wand and prodded the paper. Nothing happened, and Fred skeptically raised an eyebrow at him.
"I think you're just going to have to admit you messed up big this time. Seriously. Imagine! Generations of troublemaking students' confiscated stuff, and you grab a useless piece of paper!" Jabbing at it with his wand, he cried, "Look at it! It's absolutely blank. We should throw it in the fire and be done with it. Its a disgrace to the reputation that we, Fred and George Weasley, have so painstakingly achieved in this school!"
Picking up the parchment, Fred held it over the fireplace, only to snatch it back in shock. "Blimey! George, look!" There on the paper, lines of neat cursive were appearing rapidly. George grabbed the parchment from his twin's hand and both of them stared at it eagerly.
Mr. Moony would like to commend Messrs Fred and George Weasley for gaining possession of this artifact, and sincerely hopes that they figure out how to use it.
Mr. Padfoot agrees with Mr. Moony, and strongly recommends against throwing it in the fire as that would rob them of valuable information and opportunities.
Mr. Wormtail echoes the sentiments of both Mr. Moony and Mr. Padfoot, and wishes you all success in unlocking its secrets.
Mr. Prongs would be happy to point the young misters in the right direction, and suggests that they try spelling their intentions as to what they'd use this for out loud.
George clapped Fred on the back and snickered. "So much for this being useless, eh? Say you were wrong, or you're never seeing this again!"
Fred sighed. "Alright, alright, I admit it. You were right. Now all we have to do is figure out what exactly this thing does. It did say to spell out our intentions... Hmm. Fine then. I promise to use whatever this is to perpetuate harmony and goodness throughout the wizarding world!"
Four new sentences appeared:
Mr. Wormtail thinks that Messrs Fred and George Weasley are full of it, and advises them to tell the truth.
Mr. Padfoot sadly shakes his head and regrets to inform Messrs Fred and George Weasley that they aren't of a suitable temperament and also asks them to learn to lie better.
Mr. Prongs would like to call attention to the fact that the four creators, namely themselves, had a long history of detentions and lines during their time at Hogwarts thanks to following their beliefs.
Mr. Moony would merely like to state that the parchment in question is capable of sensing your true natures, and that the only reason we are still conversing with you is because you show great promise.
For the second time that night, Fred got smacked hard, this time on the back of his head. "You idiotic git! Let me try. I promise to someday push Filch into the Vanishing Cabinet!"
And so the night wore on, with the twins trying various phrases and the Map replying to them, alternating between hints, sarcasm, insults, and wry bits of advice. A few choice examples follow below:
Mr. Padfoot appreciates your desire to wreck havoc and wishes he could share a pint of Butterbeer with you.
Or:
Mr. Wormtail prays that Messrs Fred and George Weasley manage to someday trick Mrs. Norris into eating an Acid Pop.
Once:
Mr. Prongs is pleased to tell you that you are getting warmer and would love to meet you someday to discuss a prank he has in mind.
And hours later, finally:
Mr. Moony hopes that the twins are up to no good, and suggests that they solemnly swear the same, and see what happens.
Fred and George were generally patient people, but after all this time fruitlessly trying, even they couldn't take it. George glared at the Map, and if he could, he would have probably burned holes into it with his eyes. Fred was just as irritated, and he exclaimed exasperatedly, "I can't believe it! We've been trying for what seems like an eternity! We've used every combination of promises to make mischief that we could think of, and nothing works!"
Poking at it, he continued, "Look at that bloody last line! What does it want me to say, that I solemnly swear that I am up to no good?" He looked down at it, scowling, only to freeze. George, seeing his brother's reaction stared at the map as well, and both the twin's jaws dropped open as they gazed at the rapidly forming Map before them.
"Messrs Moony, Wormtail, Padfoot, and Prongs congratulate Messrs Fred and George Weasley for finally figuring it out, and recommend that they say 'Mischief Managed' when they are done using it.
We are proud to present to you:
THE MARAUDER'S MAP"
The twins grinned at each other and chorused in unison, "Well, that wasn't so hard."