"Teacher, aren't scientists and doctors the same thing"
"Well, sometimes they can do the same thing, but they really are two different things."
"Well don't they both help people?"
"Sometimes." I tried to explain what the role of a scientist was and how that there are many different types of scientists.
One boy chimes in, "They blow up houses."
*Insert confused look here and then light bulb going off look as I realized this kid probably has only seen cartoons of scientists, most of whom do blow up their houses. Before long my poor mislead class was shouting out all that they knew about scientists.
"And they had crazy white hair!"
Someday in the future I will have to schedule a talk on what a real scientist does... and looks like. :)