Poll of the Week: Reflecting Humanity

Star Trek has given us lots of things over the years, including five series, with their own ship, and their own crew. And there were many things common to all of these crews, but one particular thing was worth noticing: Each of them had a character alien to humanity, on a personal quest to either understand or become more similar to one of us.
While this was their personal objective in the series, their roles for all of us were different. They allowed us, or even forced, to look at ourselves from a different perspective. To review all of those behaviours that we give for granted, as part of our own nature, and look at them from the eyes of an alien with a different way of understanding the world. For us, these characters were a mirror on which we could see our own reflection, and maybe look at ourselves with a new light.
Now we ask, from all those characters, which do you feel better accomplished this job? Which gave us a better, deeper reflection on humanity? Tell us in the forums!
Here you go with a new General Trek question, where we discuss the series and their characters.