I like to make up weird theories in my head about it not being aliens but alternate earth people. What if every time it is actually a first-time visitor not knowing what it's like here. They don't expect us to have anything capable of bringing their experimental craft down and we do, to their surprise. Hence they always have different looking craft, different looking bodies, etc.
One thing that's been nice on Lemmy so far is we can actually discuss polls without all the top level posts being something along the lines of "Don't listen to polls, VOTE!".... as if anyone who subs to the politics section of a social media site doesn't know voting is important.