Okay so the Marauders + the Beatles has always been, like, my favourite combo ever but just stop a minute and imagine the first time Sirius Black hears a Beatles song.
Maybe it comes after a particularly difficult conversation in the aftermath of the discovery of the Furry Little Problem. Remus has sunk into himself a little and is sitting on his four-poster, with Sirius sitting opposite him looking at him with sad eyes. There’s only one thing for James to do. He heads over to the muggle record player - Sirius had been longing for one for the dorm since the minute he saw a picture of one, and James had managed to persuade his parents to buy one and send regular instalments of records randomly selected from their nearest muggle store. He’s been sent one only the week before, a few years old and by a certain band from Liverpool, and now seems a good time to try it out, so that’s what he does.
It’s one with a little energy - perhaps Can’t Buy Me Love or She Loves You or Help! if you want something fitting. For a few moments Sirius just sits in astonishment because Merlin’s Beard, what is this magic??
And then before Remus knows what’s happening he’s being pulled swiftly to his feet and swung wildly around the middle of the dormitory as Sirius grabs the nearest person and starts an insane energetic swinging dance.
James blinks for a few seconds and then begins to laugh, rolling his eyes at his best friend, before offering a hand to Peter with a charming May I have this dance?
The dormitory descends into joyful chaos as four boys swing and jive and occasionally swap partners, all while Lennon and McCartney belt out choruses. Eventually Remus is back with Sirius, being swung low over the bed, and as the song ends the expression on Sirius’s face gets a mischievous edge to it. Remus only has time for a startled uh oh before he is dropped the few inches onto the mattress and the tickle fight begins. The grin on James’s face transitions to a mirror image of Sirius’s and, despite Peter’s best efforts, it’s all Remus can do to reach behind him and grab a pillow to ward off his attackers.
The resulting pillow fight lasts until all four boys are completely exhausted, and they slump down in a heap of tangled limbs on the wooden floor of the dormitory, panting and laughing. Just when Remus feels as though his happiness could not get any more, he feels a gentle hand take hold of his. Looking to his right he sees Sirius Black smiling at him. Not smirking, not grinning, but smiling, the pure, warm, radiant smile that Sirius saves for only the most special moments.
Remus looks at him and gives him his own rare smile: the smile of perfect, untouched happiness that he has not smiled for a very long time.