Is it neighborhood brawl day? That's a holiday that randomly spawns on the calendar. I think it's awesome, but if you don't you can just delete it like you would any other holiday.
EDIT: Never mind, there's the answer:
"EmmaVane;c-17878993" wrote:
Windenburg has a random NPC role called "Brawler" - They start fights with active sims. It's one of the neighbourhood quirks, like the unique greetings (cheek kissing etc). I think it uses similar code to the fighting sims you see when on patrol as a police office in Detective career, except they attack your sims instead of other sims in the neighbourhood.
IL has unique things too, like neighbours bringing you food or putting out fires. StrangerVille has the infected sims and SIBs (Sims in Black).
I like these details because it adds a little uniqueness to the sims in the world, in addition as to the uniqueness of architecture, terrain and weather.
EL has special roles added to premades which you can add to any sim via cheats (or get added to randoms if that sim dies). Bess's investment scams opportunities, Knox's green crusade etc.