Well though I have my serious suspitions about what the government is hiding, and yes I have heard that they're hiding something from a program on the discovery science channel, I'm not sure whether they visit us or not.
What I can't understand is why people are still askign whether aliens exist. I mean isn't it obvious? It's such a huge universe that it would be impossible for other life beyond earth not to exist.
What shape or form it might have taken, I don't know. I don't know their intelligence level either and whether they are anything like mammals, fish, amphibians etc etc or even like plants. Everything developed from a few single cells so everything adapts according to its surroundings.
Hope I helped tc! :)
Taking a huge interest in this field! =]