Life is interesting because you don't know what you'll find or what might happen.  With the "hidden tomb" lot setting, fog emitter, the processor, and tomb objects, there are many ways to add a touch of the unexpected to a world. Here are just a few ideas.

In a cheap apartment, turning on the TV could short out all electronics and send the sim to reset them via a switch in the utility room.  Hidden lots can contain hidden riches only seen by the sim who wanders by at just the right angle.  Flame fruits by the science lab might evolve a self-defense system that sets all sims daring to approach on fire.   Create a mysterious, ancient circle of floor switches so the player has to recruit a group to activate them all at once and find out what they do.  Build an isolated site of high paranormal activity.  Create a puzzle and give hints to the solution in different lots.  Wander into a trap from which the only escape is a visit from the Grim Reaper.

The game is much more fun when you don't know what delights or dangers you'll encounter today!