@CuriousSim The festivals are always full of wacky incidents in my games.
The Romance festival is always full of angry and sad Sims in my game, because a lot of married couples participate, then go and flirt with just about everyone. This festival is an effective marriage breaker despite its intended purpose being quite the opposite - to inspire romance and love and make Sims happy. I assume.
The Spice festival goers are all uncomfortable, because they spend the entire evening burning their mouth on spicy food.
The Humor and Hijinks festival is where most firework accidents happen in my game, leaving people all sooty and stinky which is pretty entertaining.
GeekCon and the Flea Market are actually the most peaceful and relaxed events now that I think about it. But okay, at GeekCon your Sim will do nothing aside from using the gaming pad over and over. Not that much fun. On the other hand, the Flea Market sometimes have some rare collectibles for purchase which is awesome.