Modern MaraudersAU where everything is the exact same but somehow they have phones and bereal (don’t ask me how or why I Don’t Know).
But imagine the CHAOS that ensues every time that notification pops up. Students clamoring to take Bereals with the squid, Bereals with Hagrid, Bereals from the top of the Astronomy Tower. The professors all just resigning themselves to the fact that they are at the mercy of this god forsaken app and this timer that they cannot control (no matter how many charms Flitwick attempts to put in place).
Every professor, except McGonnagall, who threatens detention for every student that attempts to pull out their phone to take the photo. This, of course does nothing to deter their enthusiasm and only makes the students more daring as they attempt to get the photo when she isn’t looking (bonus if they manage to catch her in the background).
No student is as daring as Sirius, who, upon noticing the notification, signals to his classmates to get in position as he calls Minerva over to observe his latest attempt at their transfiguring assignment. While they all get into their various poses, she examines his half-assed attempt at turning a teacup into a toad. With only 30 seconds left on the timer, he whips out his phone and snaps a selfie with her, and gets the most marvelous photo of his class on the back camera. He posts it without even so much as glancing at it, knowing he’d never get another shot at it again.
Sirius hopes that he was quick enough that maybe, just maybeeeee, Professor McGonagall wouldn’t even quite notice. Unfortunately for him, his classmates picked rather conspicuous poses that were a little hard to miss. Sirius and Remus’s attempt to quietly drop Pete from where he was hoisted on their shoulders was perhaps what gave it away. Or maybe it was Lily’s head retreating from where she posed in the middle of the heart Marlene and Mary formed with their arms. Or perhaps it was the various other students attempting to scurry back to their seats from where they were perched on their desks, or on each other, in their pursuit of the best photo possible.
If you ask any student from that class, they’d say that their part in that photo was quite worth every detention, simply from the reactions they received from their peers when they found out that they got a BeReal with McGonagall in it. Even Dumbledore couldn’t help a chuckle when he saw the shocked face of Minerva grace his screen that day.
For the rest of Sirius’s time at Hogwarts, getting a BeReal with Minnie is known as his Magnum Opus.