It's a simple question, that wakes many questions : What if alien life visited our planet, and they were humans too? What would it mean (for us and for them as well)? How would our idea of the universe and life change? How would people react? How would you react?

This question popped into my mind today and I realized I had never heard any discussion of the topic and the possibility of it. The only resemblance of the topic I can remember was in some Star Trek : The Next Generation - episode, where they explained why all the characters in the show had humanoidish - appearance like humans do. This was because all the more advanced species - humans, klingons, vulcans etc. - had a common ancestor. ( Also a pretty clever way to justify the fact that they all just looked like humans in neat cosplay costumes ).