The Little Things.
The pull strings for their dorm's ceiling light are tied up shorter to accommodate Remus' height.
They charmed the window so James' side of the blinds are always opened and Sirius' side are always closed.
Peter has chalkboard he pinned to the wall for all his daily reminders, though he'll almost always walk up to little notes from the others reminding him how loved he is.
They convinced the house elves to prepare meals full of protein on the nights following the full moon, Remus is still oblivious but is always grateful for the extra meat.
Peter hates crust on his sandwiches, luckily that's James' favourite part. They don't even have to talk about it anymore, James will just take the crusts from him every morning.
James doesn't actually care much for the crust, he just loves to see Peter's smile.
Sirius hates his bed being made because childhood trauma tm, so anytime the house elves make it the others purposefully mess it up before he sees.
Sirius peels everyone's oranges at the table because that's how he shows his love.
Remus reads before bed every night, sometimes when they've all had a hard day he reads aloud until the others fall asleep.
James will sometimes turn into a stag to amuse the others when they're sad, mostly in the confines of the dorm (but sometimes not, they've had some close calls)
Peter can't swim, so the others take turns letting him piggyback on them when they spend a weekend in the black lake.
James' mum invites them to stay literally every single break. Sirius is the only one who does, but the offer always warms Remus and Peter's hearts.
The Marauders spent a weekend exploring london once when James finally learned how to apparate. He brought them to all the wizarding places he used to go as a kid since none of the others got to.
The closer they got to graduating the more of a mess James always was, there were many days the others would need to carry him down the hall to their next class from how hard he was crying.
After every full moon when Remus finally got to sleep in his own bed, he found his nightstand covered in chocolates and his favourite books.
Whenever Sirius recieved a letter from home the others would take turns reading it in ridiculously dramatic voices until they could get him to smile.
Whenever any of them would get made fun of they would incite a game they called "the roasting party" where they would all take turns making fun of each other and laughing until none of it hurt anymore.
Every Christmas they exchanged secret Santa presents and every year Sirius went last so he could watch the fear on their faces when they realised who drew their name. (He was well known for his gag gifts)
Remus always knew he wanted to be a professor when he grew up, but he never thought it would be possible because of his condition. So for the final week of Seventh year the rest of the Marauders convinced all of the staff to refer to him ONLY as Professor Lupin just to see him smile.
