What happens when I use the genie lamp on Sims 2?

ok so a few days ago i bought a genie lamp, clicked "make a wish" and then one of the sims were set on fire. btw im playing on my PS2. anyways why did this happen? what are the positives and negatives about it? and what happens when u talk to the genie? im playing storymode and at tranquility falls. ok thanks haha :)