What would thier world look like?

I've been wondering this for a while.. From what the aliens look like (let's just say they actually do look like those short, gray, big eyed and slit mouth ones people claim saw) what would their planet look like?

Since they would have to be adapted to their world, what kind of environment would they had to endure and adapt to look like that?

Light, gravity, weather conditions etc...

wow.. the possibilities are endless. This question really cant be answered with certainty because no one really knows. But you are not the only one looking for this, many of us here want the same answers. But then again, what we think aliens and their worlds look like are mostly up to us, since most have never seen one, everyone has their different thoughts that make sense to them.