On the anniversary someone could start a thread entitled “20 YEARS OF DIS” and then people could comment about what it means to them. Then after about 35 posts it can descend into a fight about something no one understands, and someone will announce they are leaving in a giant harrumph, while everyone else gathers round showing support, even though no one really knows what it was all about. Ultimately the thread gets closed by moderators for mental health reasons.
That sort of thing.