Students out after curfew from all four houses playing hide and seek in Hogwarts.
Like there can be a person from each house who had to find everyone. Like Gryffindors have to find Ravenclaws, Ravenclaws have to find slytherins, slytherins have to find hufflepuffs, and hufflepuffs have to find Griffyindors.
And then just for this one night, there is no house competition, no rivalries, nothing. Just kids having fun