Do it again. But with more fire.
I remember playing Sims 1, and shoving tons of bushes inside around the fireplace just to cause firesAahhh memories.
So, my sim is in his bedroom, painting, when all of a sudden a part of the living room floor spontaneously combusted. WTF. Apparently, putting fireplaces on wooden floors is a bad idea. It just left ashes, though, nothing was even damaged.