Not a one-shot. Plan was 2-4 sessions. I estimate the total playtime was probably about 6ish hours spread over three session. Still quite a lot of work for such a short experience, but not as hard as it sounds. I made a spread sheet to stat the NPCs, and the vast majority of them were based on a real-life celebrity, so it was easy to pop stats into each entry of the 40. A few of the characters would become "faction leaders" as things devolved to chaos, and I loosely grouped them that way--assuming that the faction leader is EVEN ALIVE when shit hits the fan.40 NPCs with their own plots and schedules? For a one-shot? You, sir, are a genius or a madman. I live in fear of your three ring binders.
Simpler than it sounds to prepare. The hardest part was "Choreographing" the End of the World Party, which had all the guests in different rooms at different times doing different things.