Yeah, I'm gonna throw some of the stuff from ROM into there - like how a potion backfire, with the black smoke and passed-out sims, could be terrifying to an unsuspecting bystander in the real world. Also, while funny in-game, some of the vampire powers would again be terrifying. It's weird thinking of this stuff in the context of real life - most of it's just funny or quirky in-game.
Oh lord - the cowplant. It's huge to a sim, and actually EATS PEOPLE. Like some kind of immovable triffid. And the luring-by-basically-hypnotic-cake thing would be scary as well. As well as the whole male-pregnancy-by-alien-abduction thing - what is WITH that? It's one of my favorite game mechanics, but if you think about it it's actually pretty messed up.
Edit: I used hyphens ( - ) way to much there, not sure why.
Edited twice for typos.