I like the idea that it's actually "a cap from Super Mario brothers".
I believe in the possibility of other intelligent life aside from humans (you can't argue with centuries of proof), but as for flying saucers just randomly feeling the need to fly through the sky for no apparent reason...I don't think humans are really so interesting. Maybe the idea of aliens comes from the need for humans to believe that there is something in this universe greater than oneself. But, of course, that's just my opinion.
It's unreasonable to deny the possibility of extraterrestrial life. Apparently, microbe fossils have been found inside a meteorite. However, I see no reason to think that UFOs are alien spacecraft. People want to believe all sorts of weird stuff. Maybe they just want to inject a little fantasy into their humdrum lives.