Like approximately 3.7 billion other people, we freaking loved the Marauder's Map when we first discovered it in Prisoner of Azkaban.
We gushed about it, writing,
Seriously, how cool is the Marauder's Map? It's pretty darn cool. First off, what does Marauder mean, though? That's a good SAT word to know. "Marauder" means a looter, an outlaw who roams about pillaging and plundering. So, like a pirate, basically.
But Harry Potter and the Cursed Child takes the Marauder's Map and shows Harry using it to monitor his own son. Harry is pillaging and plundering his son's freedom and trust, which is a lot more painful to watch than if the map had been put through a shredder in Hermione's office.
Not only does Harry use it to spy, he bullies McGonagall into using it to spy on Albus. Doing this basically turns the Marauder's Map into the all-seeing Eye of Sauron. All that's missing is a blast of deadly magic turning Albus into a greasy stain on Hogwarts cobblestones if he's even in the same wing as Scorpius Malfoy.
"I solemnly swear that I am up to no good," takes on a whole new meaning. It's Harry's militant parenting that is no good.