Okay, another of my head canons...

SPOILER ALERT (sort of, DON'T READ UNLESS YOU'VE READ THE DEATHLY HALLOWS)

George and Angelina having twin boys and naming them Fred and George Jr, and them going to school with James and the three of them becoming an inseparable trio, and hiding out in the Room of Requirement (which turns into a huge bunker perfect for hiding from Filch and planning their next joke session), and raiding Weasleys' Wizard Wheezes on weekends, and Lily, Albus, Rose and Hugo sort of tagging along with them until they decide to form their own clique with Luna and Neville's daughter (you guys think of a name for her) and waging war on them.

HP fandom.